Add macOS CI coverage

[Widthdom]

CLOSES #224

Summary

• add a blocking test-macos job on macos-latest for all pull requests, supported-branch pushes, and manual runs already configured by the main CI workflow
• build Release and run the stable test suite, excluding only hosted-runner-sensitive E2E and timing-sensitive Performance tests
• execute the generated macOS apphost non-interactively and verify executable permission, --doctor tool discovery, temporary POSIX paths with spaces, case-variant path handling, report artifacts, and reportable-difference exit code 5
• upload macOS TRX results and bound runner cost with a 20-minute timeout
• document the narrow exclusions and deferred real-disassembler macOS E2E in English and Japanese

Acceptance criteria

• macos-latest performs a Release build
• the stable suite runs with only E2E and Performance excluded
• a non-interactive CLI smoke verifies outputs and exit behavior
• exclusions are narrow and documented with reasons
• the existing PR/push/manual triggers are reused and job cost is bounded by a timeout
• the named macOS job is visible and blocking because it has no job-level condition or continue-on-error

Verification

• dotnet test FolderDiffIL4DotNet.Tests/FolderDiffIL4DotNet.Tests.csproj --configuration Release --nologo --filter FullyQualifiedName~DotNetWorkflow_BuildsAndSmokeTestsOnMacOs (1 passed)
• macOS stable filter locally: 2,040 passed
• full Release test suite: 2,044 passed, 1 expected real-disassembler E2E skip
• direct macOS apphost smoke: expected exit 5; Markdown, HTML, and audit JSON generated; path/case assertions passed
• dotnet format FolderDiffIL4DotNet.sln --verify-no-changes --no-restore --verbosity minimal
• workflow YAML parse and git diff --check

The hosted macos-latest run on this PR is the final environment-level validation.