* upstream/main: (56 commits)
  [main] Source code updates from dotnet/dotnet (dotnet#82655)
  Update insert.yml to use roslyn-tools for insertions (dotnet#82615)
  Localized file check-in by OneLocBuild Task: Build definition ID 327: Build ID 2921538
  Localized file check-in by OneLocBuild Task: Build definition ID 327: Build ID 2921538
  Reduce allocations during source text diffing (dotnet#82462)
  Localized file check-in by OneLocBuild Task: Build definition ID 327: Build ID 2920904
  Localized file check-in by OneLocBuild Task: Build definition ID 327: Build ID 2920904
  Revert "Throw NotImplementedException when a build errorId is not supported" (dotnet#82638)
  [main] Source code updates from dotnet/dotnet (dotnet#82623)
  Revert System.ValueTuple version update (dotnet#82639)
  Pack enum values
  Track non-blocking PROTOTYPE comments for `Unions` feature in an issue (dotnet#82637)
  Update the build system errors instructions for Visual Studio 2026
  Don't log named pipe connection failures as errors in BuildServerConnection (dotnet#82609)
  Fix resx source generator for less common resx metadata and locations (dotnet#81994)
  Disallow `ref` modifier for a union declaration (dotnet#82632)
  Add IFSharpInlineHintsService2 for displayAllOverride support (dotnet#82629)
  Report errors for union members that are not permitted (dotnet#82626)
  Check language version for union matching and conversions (dotnet#82617)
  [main] Update dependencies from dotnet/arcade (dotnet#82618)
  ...