- clearChatHistory: use functional setChatHistory updater so blob URL
revocation operates on the latest snapshot, not a stale closure capture.
- Simplified mode: skip sessionStorage hydration and persistence for
messageTraceId, responsesSessionId, and useApiSessionManagement so
embedded widgets don't cross-contaminate the full playground session.
- Debounce race: skip re-writing empty chatHistory to sessionStorage
after clearChatHistory already removed the key.
- Added 5 new tests covering these fixes (39 total).
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>