Inconsistent Analyzer-Reporting behaviour local vs Build Server

### Describe the bug
we have custom analyzers. One reports classes that should be named according to modifiers (ie "abstract" -> "...Base").
This Analyzer gets triggerd on our build server (Devops on premise, MSBuild@1, msbuild location from VS 2026). However it does not get triggerd locally in Visual Studio, no matter how many (re)builds and "Run Code Analysis on Solution" is done.

### To Reproduce
- Symbol Analyzer
- context.ConfigureGeneratedCodeAnalysis(GeneratedCodeAnalysisFlags.None);
- partial class
- Entity.cs with no modifiers
- generated part with "partial" keyword inside of a "Entity.Designer.cs" file

### Exceptions (if any)

### Further technical details
details of dotnet --info

.NET SDK:
Version: 10.0.200
Commit: 40cd698e5c
Workload version: 10.0.200-manifests.b2769242
MSBuild version: 18.3.0-release-26119-122+40cd698e5

Runtime Environment:
OS Name: Windows
OS Version: 10.0.26200
OS Platform: Windows
RID: win-x64
Base Path: C:\Program Files\dotnet\sdk\10.0.200\

.NET workloads installed:
There are no installed workloads to display.
Configured to use workload sets when installing new manifests.
No workload sets are installed. Run "dotnet workload restore" to install a workload set.

Host:
Version: 10.0.4
Architecture: x64
Commit: 80d3e14f5e

.NET SDKs installed:
7.0.102 [C:\Program Files\dotnet\sdk]
8.0.419 [C:\Program Files\dotnet\sdk]
9.0.100-rc.1.24452.12 [C:\Program Files\dotnet\sdk]
9.0.205 [C:\Program Files\dotnet\sdk]
10.0.200 [C:\Program Files\dotnet\sdk]

.NET runtimes installed:
Microsoft.AspNetCore.App 7.0.2 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 8.0.25 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 9.0.0-rc.1.24452.1 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 9.0.6 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 9.0.14 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 10.0.4 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.NETCore.App 7.0.2 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 8.0.25 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 9.0.0-rc.1.24431.7 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 9.0.6 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 9.0.14 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 10.0.4 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.WindowsDesktop.App 7.0.2 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 8.0.25 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 9.0.0-rc.1.24452.1 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 9.0.6 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 9.0.14 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 10.0.4 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]

Other architectures found:
x86 [C:\Program Files (x86)\dotnet]
registered at [HKLM\SOFTWARE\dotnet\Setup\InstalledVersions\x86\InstallLocation]

Environment variables:
DOTNET_CLI_TELEMETRY_OPTOUT [true]

global.json file:
Not found

Learn more:
https://aka.ms/dotnet/info

Download .NET:
https://aka.ms/dotnet/download

- VisualStudio 2026: Insiders [11605.296]

Start by reproducing the Symbol Analyzer with context.ConfigureGeneratedCodeAnalysis(GeneratedCodeAnalysisFlags.None) against the partial Entity.cs and Entity.Designer.cs example. Compare reporting from Visual Studio 2026, "Run Code Analysis on Solution," rebuilds, and the DevOps MSBuild@1 build using the supplied .NET details. Done means the local-versus-build-server behavior is explained and the expected analyzer reporting is established.

Written by the indexing model from the issue text.