Bug: Changes views show stale content after deleting all sessions

[ravshansbox]

Problem

After deleting all sessions (when navigating back to the session list where params.id is undefined), the following views still display stale content instead of being empty:

• Session changes view
• Last turn changes view
• Changes view

Expected Behavior

All changes views should be completely empty after deleting all sessions and returning to the session list.

Root Cause

1. SessionReview component state persistence: The local store in SessionReview component is initialized with initial diffs and doesn't clear itself when diffs become empty.

2. Tree state not cleared on navigation: The tree state (which tracks activeDiff, pendingDiff, reviewScroll) is only cleared when sessionKey changes, but not when params.id becomes undefined.