Reduce stale auto-review ledger burn

[cbusillo]

Summary

• suppress terminal stale/detached auto-review findings from the compact ledger prompt context while keeping current/matching findings actionable
• add aggregate diagnostics for suppressed stale history and duplicate-review saved token estimates
• record duplicate saved-token estimates only for auto-review runs that are actually skipped/reused

Fixes #375

Validation

• cargo test --manifest-path code-rs/Cargo.toml -p code-core compact_ledger
• cargo test --manifest-path code-rs/Cargo.toml -p code-core superseded_clean_duplicate_does_not_report_saved_tokens
• cargo test --manifest-path code-rs/Cargo.toml -p code-tui auto_review
• ./build-fast.sh

Agent review

• planning agents reviewed the issue shape and recommended a focused review-store/TUI patch
• initial review agents found one medium duplicate-savings bug; fixed before final validation
• final cleanup review agents reported no blocking/high/medium issues