Settings changes can now be staged for owner review before being applied

What

• A new settings-review store, saved at .claude/state/settings-review.json, lets changes to settings files (user, project, local, and policy settings) be staged as pending proposals instead of being written immediately. When staged, the user sees a message saying the change is "Staged for your review · not applied until you accept it in /settings-review". The store supports atomic staged writes and tamper detection (comparing file identity and hash before promoting a change).
• The new state file is now included in the tracked and cleaned-up state paths, and a new cleanup routine periodically removes stale entries from the store, logging an error if cleanup fails.
• However, the logic that decides whether a write should actually be routed into this review store is hardcoded to never trigger in this build, so as shipped, nothing is actually staged for review yet.

Why

This lays the groundwork for letting an account owner review and approve settings changes (like environment variables or permission rules) before they take effect, rather than having them applied instantly. It isn't active yet in this release.