Archive superseded auto-review results

[cbusillo]

Summary

• classify Auto Review completions as current, superseded, or ignored
• archive same-session superseded findings as historical Auto Review notices without post-turn developer injection
• keep cross-session and missing-metadata completions fail-closed, and preserve active review state/locks

Validation

• cargo test -p code-tui --features test-helpers auto_review
• ./build-fast.sh

Review

• read-only agent review found two race/lock concerns; both were fixed and covered by regression tests before this PR

Refs #76