Expose workspace-check truncation metadata

[Widthdom]

Summary

• Expose authoritative truncation metadata for all six bounded workspace_check path lists.
• Preserve count/truncation signals in field projections, compact CLI/MCP output, JSON byte budgets, and safe human diagnostics.
• Add cross-target regression coverage, bilingual documentation, and the 5055.fixed.md changelog fragment.

Validation

• dotnet build CodeIndex.sln -c Release --no-restore -p:UseSharedCompilation=false
• dotnet build CodeIndex.sln --no-restore -p:UseSharedCompilation=false
• dotnet format CodeIndex.sln --no-restore --verify-no-changes --verbosity minimal
• dotnet run --project tools/CodeIndex.Changelog -- check
• Full standalone net8 suite: 11,208 passed, 7 skipped, 0 failed
• Full standalone net9 suite: 10,742 passed, 412 skipped, 0 failed
• Focused post-review cross-target suite: 30 passed on net8 and 30 passed on net9
• Broader post-review cross-target suite: 110 passed on net8 and 110 passed on net9
• Codex adversarial review: 2 rounds; all 3 first-round findings addressed, final round found no actionable defects

Base note

This branch was created from d444cfdb2c660425afda504b9998977cdf15c89e as requested; later origin/main commits were not incorporated.

Fixes #5055