Preserve audit alias command identity

[Widthdom]

Summary

• Preserve the public audit invocation context while delegating to the shared search and recipe pipeline.
• Report audit-originated parse, validation, selection, conflict, JSON, and human-readable failures as cdidx audit without leaking internal search --recipe syntax.
• Keep direct search behavior unchanged, centralize structured audit errors, honor --max-json-bytes, and use audit syntax in generated replay and cursor guidance.
• Add focused regression coverage plus bilingual README, developer/testing guide, and changelog fragment updates.

Root cause

The audit alias forwarded into the search implementation without carrying the originally invoked public command. Downstream validation, error serialization, recovery hints, and generated commands therefore reconstructed messages from the internal search --recipe path.

Validation

• dotnet build CodeIndex.sln -c Release -p:UseSharedCompilation=false — 0 warnings, 0 errors after merging the latest origin/main.
• Issue Report audit alias errors with audit usage #4875 tests on net8.0 and net9.0 — 2/2 passed on each target after the merge.
• Search/audit regression tests on net8.0 and net9.0 — 262/262 passed on each target.
• Full net8.0 suite — 10,809 passed, 7 skipped, 0 failed.
• Full net9.0 suite — 10,334 passed, 420 skipped; one unrelated watcher timing test failed during the concurrent run and passed immediately in isolated net9.0 retry (and on net8.0 and origin/main).
• dotnet format CodeIndex.sln --verify-no-changes --no-restore.
• Changelog validation — 49 fragments validated.
• Repository index — fresh at the PR head, 1,275 files, 0 warnings/errors.
• Mandatory codex review --base origin/main — two adversarial-review iterations completed; all four actionable findings were fixed and their exact reproductions are covered.

Follow-up candidates

None.

Fixes #4875