Edit Plan Endpoint

Edit an existing plan based on user feedback.

This endpoint:

1. Takes the current plan and user feedback
2. Optionally accepts previous edit requests for context
3. Streams the revised plan tokens via Socket.IO
4. Returns the complete revised plan

Args: session_id: Session ID for Socket.IO room current_plan: The current plan text to edit feedback: User's feedback/edit request edit_history: Optional JSON array of previous feedback messages current_user: Authenticated user info

Returns: PlanResponse with the revised plan text