Annotate Arcade MSBuild tasks with [MSBuildMultiThreadableTask] to avoid TaskHost marshalling in -mt builds

## Summary

MSBuild's multi-threaded mode (`-mt`) runs all build nodes as threads inside a single process. Any task **not** marked with `Microsoft.Build.Framework.MSBuildMultiThreadableTaskAttribute` is routed to an out-of-proc **sidecar TaskHost** for isolation, so every invocation pays cross-process serialization of its inputs and outputs.

**No task in this repository is currently annotated**, so all ~136 Arcade tasks are marshalled out-of-proc in `-mt` builds. This measurably eats into the gains from `-mt` + MSBuild Server + node reuse.

## Measured impact

A/B of the **runtime** inner repo build inside the [dotnet/dotnet](https://github.com/dotnet/dotnet) VMR (win-x64, same source SHA `2eebfbf`, same SDK `11.0.100-rc.1.26420.103`, MSBuild `18.11.0-1.26420.103`). Command lines were identical except:

- **A (baseline):** `/nr:False`, no `-mt` -> `MSBuild Server was requested but not used for this build: node reuse is disabled`
- **B:** `/nr:True -mt` -> `Reusing the running MSBuild Server node for this build`

Wall time went 51.50 min -> 49.64 min, only **1.86 min (3.6%)**. Meanwhile:

| metric | A (baseline) | B (`-mt`+server+nodereuse) |
|---|---|---|
| TaskHost invocations | 849 | **14,125** (16.6x) |
| distinct caller processes | 8 | 1 (all nodes are threads) |
| total node-busy time | 13,622 s | 12,189 s (-10.5%) |
| effective parallelism (of 8 nodes) | 4.41x | **4.09x** |
| sum of non-nesting task time | 4,026 s | **4,124 s (+98 s)** |

Engine overhead genuinely dropped (`MSBuild` task inclusive 126,987s -> 106,276s), but ~100s of that was handed straight back as TaskHost marshalling. Arcade-owned tasks are the bulk of it:

| task | A | B | ratio | invocations |
|---|---|---|---|---|
| `ChooseBestP2PTargetFrameworkTask` | 1.5 s | 17.6 s | 11.8x | 1,740 |
| `GetLicenseFilePath` | 0.4 s | 15.0 s | **36x** | 1,542 |
| `ChooseBestTargetFrameworksTask` | 0.4 s | 12.6 s | **32x** | 1,195 |
| `GeneratePackageReport` | 1.7 s | 13.6 s | 8.0x | 11 |
| `ValidateLicense` | 0.4 s | 10.8 s | **30x** | 1,542 |
| `GetLastStablePackage` | 0.1 s | 6.3 s | **61x** | 130 |
| `GenerateResxSource` | 1.6 s | 6.2 s | 3.8x | 606 |
| `GetMinimumNETStandard` | 0.3 s | 3.0 s | 10.3x | 60 |
| `ApplyPreReleaseSuffix` | 0.03 s | 2.5 s | **77x** | 109 |
| `TranslateSource` | 1.8 s | 3.1 s | 1.7x | 208 |

That is **~82 s of pure added overhead** from 10 Arcade tasks in a single repo build, and it repeats for every repo in the VMR.

## Proposed change

Audit each task and add `[MSBuildMultiThreadableTask]` where it is genuinely thread-safe.

Per [`MSBuildMultiThreadableTaskAttribute`](https://github.com/dotnet/msbuild/blob/main/src/Framework/MSBuildMultiThreadableTaskAttribute.cs), a task qualifies only if it:

- does **not** modify global process state (env vars, current working directory, etc.), and
- does **not** depend on global process state, including relative path resolution.

Most of the P1 tasks above are pure item/string transforms, so they should qualify easily.

### Implementation note

Arcade currently pins the MSBuild packages at `17.12.50` (`eng/Version.Details.props`, flowed from dotnet-msbuild), which predates the attribute. Step 1 is simply to **flow up the MSBuild package versions to 18.x** so `MSBuildMultiThreadableTaskAttribute` is available from `Microsoft.Build.Framework` directly:

```xml
17.12.50
17.12.50
17.12.50
17.12.50
```

The attribute is **non-inheritable** (`Inherited = false`), so it must be applied to each concrete task class - not to a shared base such as `BuildTask` / `MSBuildTaskBase` / `XlfTask`.

## Task inventory

All concrete MSBuild task classes under `src/` (excluding `eng/common`, abstract bases and test-only stubs). **136 tasks.**

### P1 - measured hot path (do these first)

- [ ] `ChooseBestP2PTargetFrameworkTask` - `src\Microsoft.DotNet.Build.Tasks.TargetFramework\src\ChooseBestP2PTargetFrameworkTask.cs`
- [ ] `GetLicenseFilePath` - `src\Microsoft.DotNet.Arcade.Sdk\src\GetLicenseFilePath.cs`
- [ ] `ChooseBestTargetFrameworksTask` - `src\Microsoft.DotNet.Build.Tasks.TargetFramework\src\ChooseBestTargetFrameworksTask.cs`
- [ ] `GeneratePackageReport` - `src\Microsoft.DotNet.Build.Tasks.Packaging\src\GeneratePackageReport.cs`
- [ ] `ValidateLicense` - `src\Microsoft.DotNet.Arcade.Sdk\src\ValidateLicense.cs`
- [ ] `GetLastStablePackage` - `src\Microsoft.DotNet.Build.Tasks.Packaging\src\GetLastStablePackage.cs`
- [ ] `GenerateResxSource` - `src\Microsoft.DotNet.Arcade.Sdk\src\GenerateResxSource.cs`
- [ ] `GetMinimumNETStandard` - `src\Microsoft.DotNet.Build.Tasks.Packaging\src\GetMinimumNETStandard.cs`
- [ ] `ApplyPreReleaseSuffix` - `src\Microsoft.DotNet.Build.Tasks.Packaging\src\ApplyPreReleaseSuffix.cs`
- [ ] `TranslateSource` - `src\Microsoft.DotNet.XliffTasks\Tasks\TranslateSource.cs`

### P2 / P3 - remaining tasks by package

Microsoft.DotNet.Arcade.Sdk (15)

- [ ] `CalculateAssemblyAndFileVersions` - `src\Microsoft.DotNet.Arcade.Sdk\src\CalculateAssemblyAndFileVersions.cs`
- [ ] `CheckRequiredDotNetVersion` - `src\Microsoft.DotNet.Arcade.Sdk\src\CheckRequiredDotNetVersion.cs`
- [ ] `CompareVersions` - `src\Microsoft.DotNet.Arcade.Sdk\src\CompareVersions.cs`
- [ ] `DownloadFile` - `src\Microsoft.DotNet.Arcade.Sdk\src\DownloadFile.cs`
- [ ] `ExtractNgenMethodList` - `src\Microsoft.DotNet.Arcade.Sdk\src\ExtractNgenMethodList.cs`
- [ ] `GenerateChecksums` - `src\Microsoft.DotNet.Arcade.Sdk\src\GenerateChecksums.cs`
- [ ] `GenerateSourcePackageSourceLinkTargetsFile` - `src\Microsoft.DotNet.Arcade.Sdk\src\GenerateSourcePackageSourceLinkTargetsFile.cs`
- [ ] `GetAssemblyFullName` - `src\Microsoft.DotNet.Arcade.Sdk\src\GetAssemblyFullName.cs`
- [ ] `GroupItemsBy` - `src\Microsoft.DotNet.Arcade.Sdk\src\GroupItemsBy.cs`
- [ ] `InstallDotNetCore` - `src\Microsoft.DotNet.Arcade.Sdk\src\InstallDotNetCore.cs`
- [ ] `LocateDotNet` - `src\Microsoft.DotNet.Arcade.Sdk\src\LocateDotNet.cs`
- [ ] `SaveItems` - `src\Microsoft.DotNet.Arcade.Sdk\src\SaveItems.cs`
- [ ] `SetCorFlags` - `src\Microsoft.DotNet.Arcade.Sdk\src\SetCorFlags.cs`
- [ ] `SingleError` - `src\Microsoft.DotNet.Arcade.Sdk\src\SingleError.cs`
- [ ] `Unsign` - `src\Microsoft.DotNet.Arcade.Sdk\src\Unsign.cs`

Microsoft.DotNet.Build.Tasks.Feed (12)

- [ ] `ConfigureInputFeed` - `src\Microsoft.DotNet.Build.Tasks.Feed\src\ConfigureInputFeed.cs`
- [ ] `CreateAzureContainerIfNotExists` - `src\Microsoft.DotNet.Build.Tasks.Feed\src\common\CreateAzureContainerIfNotExists.cs`
- [ ] `CreateAzureDevOpsFeed` - `src\Microsoft.DotNet.Build.Tasks.Feed\src\CreateAzureDevOpsFeed.cs`
- [ ] `CreateNewAzureContainer` - `src\Microsoft.DotNet.Build.Tasks.Feed\src\common\CreateNewAzureContainer.cs`
- [ ] `LaunchDebugger` - `src\Microsoft.DotNet.Build.Tasks.Feed\src\LaunchDebugger.cs`
- [ ] `PublishArtifactsInManifest` - `src\Microsoft.DotNet.Build.Tasks.Feed\src\PublishArtifactsInManifest.cs`
- [ ] `PublishArtifactsInManifestV3` - `src\Microsoft.DotNet.Build.Tasks.Feed\src\PublishArtifactsInManifestV3.cs`
- [ ] `PublishArtifactsInManifestV4` - `src\Microsoft.DotNet.Build.Tasks.Feed\src\PublishArtifactsInManifestV4.cs`
- [ ] `PublishBuildToMaestro` - `src\Microsoft.DotNet.Build.Tasks.Feed\src\PublishBuildToMaestro.cs`
- [ ] `PublishSignedAssets` - `src\Microsoft.DotNet.Build.Tasks.Feed\src\PublishSignedAssets.cs`
- [ ] `PushToBuildStorage` - `src\Microsoft.DotNet.Build.Tasks.Feed\src\PushToBuildStorage.cs`
- [ ] `UploadToAzure` - `src\Microsoft.DotNet.Build.Tasks.Feed\src\common\UploadToAzure.cs`

Microsoft.DotNet.Build.Tasks.FileCatalog (1)

- [ ] `GenerateFileCatalog` - `src\Microsoft.DotNet.Build.Tasks.FileCatalog\GenerateFileCatalog.cs`

Microsoft.DotNet.Build.Tasks.Installers (13)

- [ ] `CreateChangelogFile` - `src\Microsoft.DotNet.Build.Tasks.Installers\src\CreateChangelogFile.cs`
- [ ] `CreateControlFile` - `src\Microsoft.DotNet.Build.Tasks.Installers\src\CreateControlFile.cs`
- [ ] `CreateDebPackage` - `src\Microsoft.DotNet.Build.Tasks.Installers\src\CreateDebPackage.cs`
- [ ] `CreateLightCommandPackageDrop` - `src\Microsoft.DotNet.Build.Tasks.Installers\src\CreateLightCommandPackageDrop.cs`
- [ ] `CreateMD5SumsFile` - `src\Microsoft.DotNet.Build.Tasks.Installers\src\CreateMD5SumsFile.cs`
- [ ] `CreateRpmPackage` - `src\Microsoft.DotNet.Build.Tasks.Installers\src\CreateRpmPackage.cs`
- [ ] `CreateWixBuildWixpack` - `src\Microsoft.DotNet.Build.Tasks.Installers\src\CreateWixBuildWixpack.cs`
- [ ] `ExecWithRetries` - `src\Microsoft.DotNet.Build.Tasks.Installers\src\ExecWithRetries.cs`
- [ ] `GenerateCurrentVersion` - `src\Microsoft.DotNet.Build.Tasks.Installers\src\GenerateCurrentVersion.cs`
- [ ] `GenerateGuidFromName` - `src\Microsoft.DotNet.Build.Tasks.Installers\src\GenerateGuidFromName.cs`
- [ ] `GenerateMacOSDistributionFile` - `src\Microsoft.DotNet.Build.Tasks.Installers\src\GenerateMacOSDistributionFile.cs`
- [ ] `GenerateMsiVersion` - `src\Microsoft.DotNet.Build.Tasks.Installers\src\GenerateMsiVersion.cs`
- [ ] `StabilizeWixFileId` - `src\Microsoft.DotNet.Build.Tasks.Installers\src\StabilizeWixFileId.cs`

Microsoft.DotNet.Build.Tasks.Packaging (27)

- [ ] `ApplyBaseLine` - `src\Microsoft.DotNet.Build.Tasks.Packaging\src\ApplyBaseLine.cs`
- [ ] `ApplyMetaPackages` - `src\Microsoft.DotNet.Build.Tasks.Packaging\src\ApplyMetaPackages.cs`
- [ ] `CreateTrimDependencyGroups` - `src\Microsoft.DotNet.Build.Tasks.Packaging\src\CreateTrimDependencyGroups.cs`
- [ ] `FilterUnknownPackages` - `src\Microsoft.DotNet.Build.Tasks.Packaging\src\FilterUnknownPackages.cs`
- [ ] `GenerateNuSpec` - `src\Microsoft.DotNet.Build.Tasks.Packaging\src\GenerateNuSpec.cs`
- [ ] `GenerateRuntimeDependencies` - `src\Microsoft.DotNet.Build.Tasks.Packaging\src\GenerateRuntimeDependencies.cs`
- [ ] `GetApplicableAssetsFromPackageReports` - `src\Microsoft.DotNet.Build.Tasks.Packaging\src\GetApplicableAssetsFromPackageReports.cs`
- [ ] `GetApplicableAssetsFromPackages` - `src\Microsoft.DotNet.Build.Tasks.Packaging\src\GetApplicableAssetsFromPackages.cs`
- [ ] `GetAssemblyReferences` - `src\Microsoft.DotNet.Build.Tasks.Packaging\src\GetAssemblyReferences.cs`
- [ ] `GetInboxFrameworks` - `src\Microsoft.DotNet.Build.Tasks.Packaging\src\GetInboxFrameworks.cs`
- [ ] `GetLayoutFiles` - `src\Microsoft.DotNet.Build.Tasks.Packaging\src\GetLayoutFiles.cs`
- [ ] `GetPackageDescription` - `src\Microsoft.DotNet.Build.Tasks.Packaging\src\GetPackageDescription.cs`
- [ ] `GetPackageDestination` - `src\Microsoft.DotNet.Build.Tasks.Packaging\src\GetPackageDestination.cs`
- [ ] `GetPackageFromModule` - `src\Microsoft.DotNet.Build.Tasks.Packaging\src\GetPackageFromModule.cs`
- [ ] `GetPackageVersion` - `src\Microsoft.DotNet.Build.Tasks.Packaging\src\GetPackageVersion.cs`
- [ ] `GetRuntimeJsonValues` - `src\Microsoft.DotNet.Build.Tasks.Packaging\src\GetRuntimeJsonValues.cs`
- [ ] `GetRuntimeTargets` - `src\Microsoft.DotNet.Build.Tasks.Packaging\src\GetRuntimeTargets.cs`
- [ ] `GetSupportedPackagesFromPackageReports` - `src\Microsoft.DotNet.Build.Tasks.Packaging\src\GetSupportedPackagesFromPackageReports.cs`
- [ ] `HarvestPackage` - `src\Microsoft.DotNet.Build.Tasks.Packaging\src\HarvestPackage.cs`
- [ ] `NuGetPack` - `src\Microsoft.DotNet.Build.Tasks.Packaging\src\NuGetPack.cs`
- [ ] `PromoteDependencies` - `src\Microsoft.DotNet.Build.Tasks.Packaging\src\PromoteDependencies.cs`
- [ ] `SplitDependenciesBySupport` - `src\Microsoft.DotNet.Build.Tasks.Packaging\src\SplitDependenciesBySupport.cs`
- [ ] `SplitReferences` - `src\Microsoft.DotNet.Build.Tasks.Packaging\src\SplitReferences.cs`
- [ ] `UpdatePackageIndex` - `src\Microsoft.DotNet.Build.Tasks.Packaging\src\UpdatePackageIndex.cs`
- [ ] `ValidateFrameworkPackage` - `src\Microsoft.DotNet.Build.Tasks.Packaging\src\ValidateFrameworkPackage.cs`
- [ ] `ValidateHarvestVersionIsLatestForRelease` - `src\Microsoft.DotNet.Build.Tasks.Packaging\src\ValidateHarvestVersionIsLatestForRelease.cs`
- [ ] `ValidatePackage` - `src\Microsoft.DotNet.Build.Tasks.Packaging\src\ValidatePackage.cs`

Microsoft.DotNet.Build.Tasks.Templating (1)

- [ ] `GenerateFileFromTemplate` - `src\Microsoft.DotNet.Build.Tasks.Templating\src\GenerateFileFromTemplate.cs`

Microsoft.DotNet.Build.Tasks.VisualStudio (6)

- [ ] `FinalizeInsertionVsixFile` - `src\Microsoft.DotNet.Build.Tasks.VisualStudio\Vsix\FinalizeInsertionVsixFile.cs`
- [ ] `FindLatestDrop` - `src\Microsoft.DotNet.Build.Tasks.VisualStudio\OptProf\FindLatestDrop.cs`
- [ ] `GenerateTrainingInputFiles` - `src\Microsoft.DotNet.Build.Tasks.VisualStudio\OptProf\GenerateTrainingInputFiles.cs`
- [ ] `GenerateTrainingPropsFile` - `src\Microsoft.DotNet.Build.Tasks.VisualStudio\OptProf\GenerateTrainingPropsFile.cs`
- [ ] `GetPkgDefAssemblyDependencyGuid` - `src\Microsoft.DotNet.Build.Tasks.VisualStudio\Vsix\GetPkgDefAssemblyDependencyGuid.cs`
- [ ] `GetRunSettingsSessionConfiguration` - `src\Microsoft.DotNet.Build.Tasks.VisualStudio\OptProf\GetRunSettingsSessionConfiguration.cs`

Microsoft.DotNet.Build.Tasks.Workloads (4)

- [ ] `CreateVisualStudioWorkload` - `src\Microsoft.DotNet.Build.Tasks.Workloads\src\CreateVisualStudioWorkload.wix.cs`
- [ ] `CreateVisualStudioWorkloadSet` - `src\Microsoft.DotNet.Build.Tasks.Workloads\src\CreateVisualStudioWorkloadSet.wix.cs`
- [ ] `HarvesterToolTask` - `src\Microsoft.DotNet.Build.Tasks.Workloads\src\Wix\HarvesterToolTask.cs`
- [ ] `WixToolTask` - `src\Microsoft.DotNet.Build.Tasks.Workloads\src\Wix\WixToolTask.cs`

Microsoft.DotNet.CMake.Sdk (2)

- [ ] `CreateCMakeFileApiQuery` - `src\Microsoft.DotNet.CMake.Sdk\src\CreateCMakeFileApiQuery.cs`
- [ ] `GetCMakeArtifactsFromFileApi` - `src\Microsoft.DotNet.CMake.Sdk\src\GetCMakeArtifactsFromFileApi.cs`

Microsoft.DotNet.Deployment.Tasks.Links (2)

- [ ] `CreateAkaMSLinks` - `src\Microsoft.DotNet.Deployment.Tasks.Links\src\CreateAkaMSLinks.cs`
- [ ] `DeleteAkaMSLinks` - `src\Microsoft.DotNet.Deployment.Tasks.Links\src\DeleteAkaMSLinks.cs`

Microsoft.DotNet.GenAPI (1)

- [ ] `GenAPITask` - `src\Microsoft.DotNet.GenAPI\GenAPITask.cs`

Microsoft.DotNet.GenFacades (3)

- [ ] `ClearAssemblyReferenceVersions` - `src\Microsoft.DotNet.GenFacades\ClearAssemblyReferenceVersions.cs`
- [ ] `GenPartialFacadeSource` - `src\Microsoft.DotNet.GenFacades\GenPartialFacadeSource.cs`
- [ ] `NotSupportedAssemblyGenerator` - `src\Microsoft.DotNet.GenFacades\NotSupportedAssemblyGenerator.cs`

Microsoft.DotNet.Helix (16)

- [ ] `CancelHelixJobs` - `src\Microsoft.DotNet.Helix\Sdk\CancelHelixJob.cs`
- [ ] `CheckAzurePipelinesTestResults` - `src\Microsoft.DotNet.Helix\Sdk\CheckAzurePipelinesTestResults.cs`
- [ ] `CheckHelixJobStatus` - `src\Microsoft.DotNet.Helix\Sdk\CheckHelixJobStatus.cs`
- [ ] `CreateMTPWorkItems` - `src\Microsoft.DotNet.Helix\Sdk\CreateMTPWorkItems.cs`
- [ ] `CreateTestsForWorkItems` - `src\Microsoft.DotNet.Helix\Sdk\CreateFailedTestsForFailedWorkItems.cs`
- [ ] `CreateXHarnessAndroidWorkItems` - `src\Microsoft.DotNet.Helix\Sdk\CreateXHarnessAndroidWorkItems.cs`
- [ ] `CreateXHarnessAppleWorkItems` - `src\Microsoft.DotNet.Helix\Sdk\CreateXHarnessAppleWorkItems.cs`
- [ ] `CreateXUnitWorkItems` - `src\Microsoft.DotNet.Helix\Sdk\CreateXUnitWorkItems.cs`
- [ ] `DownloadFromResultsContainer` - `src\Microsoft.DotNet.Helix\Sdk\DownloadFromResultsContainer.cs`
- [ ] `FindDotNetCliPackage` - `src\Microsoft.DotNet.Helix\Sdk\FindDotNetCliPackage.cs`
- [ ] `GetHelixWorkItems` - `src\Microsoft.DotNet.Helix\Sdk\GetHelixWorkItems.cs`
- [ ] `InstallDotNetTool` - `src\Microsoft.DotNet.Helix\Sdk\InstallDotNetTool.cs`
- [ ] `SendHelixJob` - `src\Microsoft.DotNet.Helix\Sdk\SendHelixJob.cs`
- [ ] `StartAzurePipelinesTestRun` - `src\Microsoft.DotNet.Helix\Sdk\StartAzurePipelinesTestRun.cs`
- [ ] `StopAzurePipelinesTestRun` - `src\Microsoft.DotNet.Helix\Sdk\StopAzurePipelinesTestRun.cs`
- [ ] `WaitForHelixJobCompletion` - `src\Microsoft.DotNet.Helix\Sdk\WaitForHelixJobCompletion.cs`

Microsoft.DotNet.NuGetRepack (2)

- [ ] `ReplacePackageParts` - `src\Microsoft.DotNet.NuGetRepack\tasks\src\ReplacePackageParts.cs`
- [ ] `UpdatePackageVersionTask` - `src\Microsoft.DotNet.NuGetRepack\tasks\src\UpdatePackageVersionTask.cs`

Microsoft.DotNet.PackageTesting (3)

- [ ] `GetCompatiblePackageTargetFrameworks` - `src\Microsoft.DotNet.PackageTesting\GetCompatiblePackageTargetFrameworks.cs`
- [ ] `VerifyClosure` - `src\Microsoft.DotNet.PackageTesting\VerifyClosure.cs`
- [ ] `VerifyTypes` - `src\Microsoft.DotNet.PackageTesting\VerifyTypes.cs`

Microsoft.DotNet.SharedFramework.Sdk (5)

- [ ] `CreateFrameworkListFile` - `src\Microsoft.DotNet.SharedFramework.Sdk\src\CreateFrameworkListFile.cs`
- [ ] `GeneratePlatformManifestEntriesFromFileList` - `src\Microsoft.DotNet.SharedFramework.Sdk\src\GeneratePlatformManifestEntriesFromFileList.cs`
- [ ] `GeneratePlatformManifestEntriesFromTemplate` - `src\Microsoft.DotNet.SharedFramework.Sdk\src\GeneratePlatformManifestEntriesFromTemplate.cs`
- [ ] `GenerateSharedFrameworkDepsFile` - `src\Microsoft.DotNet.SharedFramework.Sdk\src\GenerateSharedFrameworkDepsFile.cs`
- [ ] `ValidateFileVersions` - `src\Microsoft.DotNet.SharedFramework.Sdk\src\ValidateFileVersions.cs`

Microsoft.DotNet.SignCheckTask (1)

- [ ] `SignCheckTask` - `src\Microsoft.DotNet.SignCheckTask\SignCheckTask.cs`

Microsoft.DotNet.SignTool (1)

- [ ] `SignToolTask` - `src\Microsoft.DotNet.SignTool\src\SignToolTask.cs`

Microsoft.DotNet.SourceBuild (4)

- [ ] `ReadNuGetPackageInfos` - `src\Microsoft.DotNet.SourceBuild\tasks\src\ReadNuGetPackageInfos.cs`
- [ ] `WriteBuildOutputProps` - `src\Microsoft.DotNet.SourceBuild\tasks\src\WriteBuildOutputProps.cs`
- [ ] `WritePackageUsageData` - `src\Microsoft.DotNet.SourceBuild\tasks\src\UsageReport\WritePackageUsageData.cs`
- [ ] `WriteUsageReports` - `src\Microsoft.DotNet.SourceBuild\tasks\src\UsageReport\WriteUsageReports.cs`

Microsoft.DotNet.SwaggerGenerator (1)

- [ ] `GenerateSwaggerCode` - `src\Microsoft.DotNet.SwaggerGenerator\Microsoft.DotNet.SwaggerGenerator.MSBuild\GenerateSwaggerCode.cs`

Microsoft.DotNet.XliffTasks (6)

- [ ] `EnsureAllResourcesTranslated` - `src\Microsoft.DotNet.XliffTasks\Tasks\EnsureAllResourcesTranslated.cs`
- [ ] `GatherTranslatedSource` - `src\Microsoft.DotNet.XliffTasks\Tasks\GatherTranslatedSource.cs`
- [ ] `GatherXlf` - `src\Microsoft.DotNet.XliffTasks\Tasks\GatherXlf.cs`
- [ ] `SortXlf` - `src\Microsoft.DotNet.XliffTasks\Tasks\SortXlf.cs`
- [ ] `TransformTemplates` - `src\Microsoft.DotNet.XliffTasks\Tasks\TransformTemplates.cs`
- [ ] `UpdateXlf` - `src\Microsoft.DotNet.XliffTasks\Tasks\UpdateXlf.cs`

/cc @dotnet/dnceng

Start with eng/Version.Details.props and the MSBuildMultiThreadableTaskAttribute definition, then audit the concrete task files listed under src/, beginning with the ten P1 files. Done means compatible MSBuild package versions are available and every genuinely thread-safe concrete task is annotated, while tasks that access or depend on process-global state remain unannotated.

Written by the indexing model from the issue text.