Fix C# type reference target resolution

[Widthdom]

Summary

• Restrict C# type_reference resolution to exact-case, type-like symbols with compatible qualifiers and generic arity.
• Leave incompatible framework and external types unresolved, preventing false reference and dependency edges while preserving exact property receiver dependencies, including inherited properties.
• Invalidate prior reference-identity candidates and retain scoped reference-graph refresh behavior.
• Keep Java reference resolution unchanged.

Validation

• dotnet build CodeIndex.sln -c Release --no-restore
• Focused regression tests on net8.0 and net9.0: 9 passed on each target
• Full net8.0 suite: 10,475 passed, 7 skipped, 0 failed
• Full net9.0 suite: 10,002 passed, 419 skipped, 0 failed
• dotnet format CodeIndex.sln --verify-no-changes --no-restore
• make lint
• dotnet run --project tools/CodeIndex.Changelog -- check
• Codex 5.6 sol xhigh adversarial review: 2 rounds, all findings addressed

Documentation and changelog

• Updated the English and Japanese sections of DEVELOPER_GUIDE.md and TESTING_GUIDE.md.
• Added changelog.d/unreleased/4825.fixed.md.

Fixes #4825