ResolvePackageFileConflicts crashes when any items have { in the path

### Describe the bug
From this SO question: https://stackoverflow.com/questions/79827986/conflict-between-microsoft-aspnetcore-and-system-security-cryptography-pkcs?noredirect=1

The customer's username (previously) was `{Username}`, and so their NuGet packages are coming from `C:\Users\{Username}\.nuget\packages`.

The task is using `string.Format` correctly to crate a conflictMessage: https://github.com/dotnet/sdk/blob/675669756ed9bb15b2d59675a897d27396098d3a/src/Tasks/Common/ConflictResolution/ConflictResolver.cs#L173-L175

However, it then passes this as a format string to Logger.LogMessage: https://github.com/dotnet/sdk/blob/675669756ed9bb15b2d59675a897d27396098d3a/src/Tasks/Common/ConflictResolution/ConflictResolver.cs#L190-L191

https://github.com/dotnet/sdk/blob/675669756ed9bb15b2d59675a897d27396098d3a/src/Tasks/Common/ConflictResolution/ConflictResolver.cs#L354-L358

https://github.com/dotnet/sdk/blob/675669756ed9bb15b2d59675a897d27396098d3a/src/Tasks/Common/Logger.cs#L103-L106

So, `string.Format` is eventually called with `{Username}` as part of the format string and throws an exception.

### To Reproduce

Create a project that has at least one PackageReference, set the environment variable `NUGET_PACKAGES` to something like `C:\{packages`, then try to build the project.

Note that Windows allows `{` in file and directory names.

### Exceptions (if any)

```text
// Source - https://stackoverflow.com/q/79827986
// Posted by RandomSkinCreator, modified by community. See post 'Timeline' for change history
// Retrieved 2025-11-25, License - CC BY-SA 4.0

dotnet build
Restore complete (0.2s)
MyApi net10.0 failed with 1 error(s) (0.0s)
C:\Program Files\dotnet\sdk\10.0.100\Sdks\Microsoft.NET.Sdk\targets\Microsoft.NET.ConflictResolution.targets(40,5): error MSB4018:
The "ResolvePackageFileConflicts" task failed unexpectedly.
System.FormatException: Input string was not in a correct format. Failure to
parse near offset 103. Expected an ASCII digit.
at System.Text.ValueStringBuilder.AppendFormatHelper(IFormatProvider provi
der, String format, ReadOnlySpan`1 args)
at System.String.FormatHelper(IFormatProvider provider, String format, Rea
dOnlySpan`1 args)
at Microsoft.NET.Build.Tasks.Logger.CreateMessage(MessageLevel level, Stri
ng format, String[] args)
at Microsoft.NET.Build.Tasks.Logger.LogMessage(MessageImportance importanc
e, String format, String[] args)
at Microsoft.NET.Build.Tasks.ConflictResolution.ConflictResolver`1.Resolve
Conflict(TConflictItem item1, TConflictItem item2, Boolean logUnresolvedConfl
icts)
at Microsoft.NET.Build.Tasks.ConflictResolution.ConflictResolver`1.Resolve
Conflicts(IEnumerable`1 conflictItems, Func`2 getItemKey, ConflictCallback`1
foundConflict, Boolean commitWinner)
at Microsoft.NET.Build.Tasks.ConflictResolution.ResolvePackageFileConflict
s.ExecuteCore()
at Microsoft.NET.Build.Tasks.TaskBase.Execute()
at Microsoft.Build.BackEnd.TaskExecutionHost.Execute()
at Microsoft.Build.BackEnd.TaskBuilder.ExecuteInstantiatedTask(TaskExecuti
onHost taskExecutionHost, TaskLoggingContext taskLoggingContext, TaskHost tas
kHost, ItemBucket bucket, TaskExecutionMode howToExecuteTask)

Build failed with 1 error(s) in 0.5s
```

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

- The IDE (VS / VS Code/ VS4Mac) you're running on, and its version