Add run_context to agent tool calls for FE run logging

- AgentTriggerRequest accepts optional agent_id (FE's stable electron-store UUID)
- _make_agent_executor injects run_context into every tool_call frame
  so Electron can attribute actions to the correct agent run
- run_local_agent accepts run_context and sends a run_complete WS frame
  when the run finishes so the FE can close the run record
- trigger_agent_run builds run_context with run_id=run_log.id and the
  stable agent_id, passes it through to run_local_agent

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

app/api/routes/agents.py

@@ -190,8 +190,11 @@ async def trigger_agent_run(
         enabled=True,
     )
 
+    # Use the FE's stable agent_id if provided, fall back to the ephemeral config id.
+    stable_agent_id = body.agent_id or config.id
+
     run_log = AgentRunLog(
-        agent_id=config.id,
+        agent_id=stable_agent_id,
         agent_type="local",
         user_id=current_user.id,
         status="running",
@@ -200,8 +203,14 @@ async def trigger_agent_run(
     await db.commit()
     await db.refresh(run_log)
 
+    run_context = {
+        "type": "agent_batch",
+        "run_id": run_log.id,
+        "agent_id": stable_agent_id,
+    }
+
     asyncio.create_task(
-        run_local_agent(current_user.id, config, run_log, device_manager)
+        run_local_agent(current_user.id, config, run_log, device_manager, run_context)
     )
 
     return _to_run_log_response(run_log)