- Implement loadChatHistory(agentId) and saveChatHistory(agentId, messages)
using localStorage key matrix:chat:<agentId> with 100-msg cap
- Each message stored with timestamp, displayed as [HH:MM] prefix
- appendChatMessage now persists to localStorage on every call
- Restore chat history on page load via renderChatHistory()
- Add clearChatHistory() and "CLEAR HISTORY" button in UI
- Wire websocket.js and session.js chat messages through appendChatMessage
for persistence of both user sends and assistant responses
Fixes#43
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>