Add comprehensive tests for the cleanup patterns used to prevent
memory leaks in long-running sessions:
- Task description cache with TTL expiration
- Promise callback null-after-rejection pattern
- Event listener tracking and removal
- DOM handler storage for frontend cleanup
- Timer/interval management
- Map cleanup patterns and safe iteration
- WeakRef/WeakMap usage patterns
- Cleanup order verification (LIFO)
Update CLAUDE.md with reference to new test file.
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>