Enforce auto review dedupe freshness policy

[cbusillo]

Summary

• make Auto Review duplicate lookup target-aware so stale detached or older snapshot runs are not reused for the active checkout
• keep diff fingerprints based on effective diff content, while preserving snapshot/head/epoch evidence separately for applicability checks
• keep adopted in-flight reviews visible by retargeting the TUI to the adopted run and replaying terminal statuses safely
• promote healthy long-running reviews to LongRunning freshness in TUI and exec status writers

Validation

• cargo test --manifest-path code-rs/Cargo.toml -p code-core duplicate_lookup
• cargo test --manifest-path code-rs/Cargo.toml -p code-core auto_review_freshness_classifier
• cargo test --manifest-path code-rs/Cargo.toml -p code-tui auto_review_diff_fingerprint
• cargo test --manifest-path code-rs/Cargo.toml -p code-tui adopted_background_review
• ./build-fast.sh

Fixes #329