- Add saved_sessions table and CRUD endpoints (save, list, resume, update, delete)
- Save is instant (no LLM summarization), stores exact conversation with tool calls
- Resume loads full message history into chat UI, sends transcript to agent on first message
- Auto-save updates DB after every agent response once a session is saved
- Delete old filesystem-based session/group management (sessions router, useChatSessions, useChatGroups)
- Clean up ChatHeader, SessionList, ChatDetailPanel for saved sessions flow
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>