feat: send live flow context to AI Assist for full editor awareness

The AI panel now sends the current tree structure (troubleshooting) or
steps + intake form (procedural/maintenance) with each message. This
gives the AI full visibility into node details, questions, descriptions,
options, and intake form fields — not just the node ID.

- Backend: add flow_context param to schema, endpoint, and service
- Frontend: add getFlowContext callback to useEditorAI hook
- TreeEditorPage: passes treeStructure as flow context
- ProceduralEditorPage: passes steps + intakeForm as flow context

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend/app/api/endpoints/ai_chat.py

@@ -172,6 +172,7 @@ async def post_message(
             session, data.content, db,
             action_type=data.action_type or "open_chat",
             focal_node_id=data.focal_node_id,
+            flow_context=data.flow_context,
         )
     except Exception as e:
         logger.exception("AI chat message failed: %s", e)