Fix suggestion category completion registry

[Widthdom]

Summary

• Drive CLI suggestion-category metadata and all generated shell completions from SuggestionRecord.ValidCategories.
• Keep default and full MCP catalog metadata synchronized with the same ordered 14-value registry.
• Add runtime, help, MCP, and process-backed cross-shell regression coverage plus bilingual testing and changelog documentation.

Validation

• Release and Debug builds passed with 0 warnings and 0 errors.
• Focused regression tests passed on net8.0 and net9.0 (32/32 each).
• Full net8.0 suite: 12,165 passed, 9 skipped, 0 failed.
• Full net9.0 suite: 11,677 passed, 433 skipped; the sole failure was the known unrelated allocation-probe flake tracked by Stabilize C# regex allocation regression probes under full-suite load #5244, and its isolated rerun passed.
• Changelog-fragment validation and git diff --check passed.
• Root and workspace index health checks passed.
• Codex adversarial review completed; the first-round findings were addressed and the final round found no blocking/actionable issues.

Follow-up

• Stabilize C# regex allocation regression probes under full-suite load #5244

Fixes #5235