- Added SWITCHER_TOGGLE message type (8) for reprocessing last user message with active switchers
- Backend: Handler fetches last user question from DB, mutates message in-place, injects switcher prompts into system_prompt
- Backend: Switcher replays skip message_history save to avoid duplication
- Frontend: toggleSwitcher() sends SWITCHER_TOGGLE when input empty, sendMessage() when text present
- Frontend: Added TOOL_EXEC and SWITCHER_TOGGLE to MessageType constants
- Fixed session_id shadowing bug in DB query (used session_id_for_query)
- Preserves conversation history for LLM context when reprocessing with switchers
