fix(agent): align /dispatch with MasterAgent.handle_message signature

The router was calling handle_message(user_id, message, context, session_id)
but MasterAgent accepts (user_id, channel_id, message, directive_id) and
returns MasterResponse{response, status, ...} with no .reply or
.agent_reports fields. Discuss DMs to the bot crashed with TypeError.

Now the router:
- Derives directive_id from session_id (or generates one)
- Pulls channel_id out of req.context
- Maps MasterResponse.response -> DispatchResponse.reply
- Returns an empty agent_reports list (the field is reserved for future use;
  per-agent reports aren't part of MasterResponse)

agent_service/routers/dispatch.py

@@ -4,6 +4,7 @@ import hashlib
 import hmac
 import logging
 import time
+import uuid
 from typing import Optional
 
 from fastapi import APIRouter, Depends, HTTPException, Request, status
@@ -73,13 +74,16 @@ async def dispatch(req: DispatchRequest, request: Request):
     settings = get_settings()
     timeout = settings.directive_timeout_minutes * 60
 
+    directive_id = req.session_id or uuid.uuid4().hex
+    channel_id = req.context.get('channel_id') if isinstance(req.context, dict) else None
+
     try:
         response = await asyncio.wait_for(
             master.handle_message(
                 user_id=req.user_id,
+                channel_id=channel_id,
                 message=req.message,
-                context=req.context,
-                session_id=req.session_id,
+                directive_id=directive_id,
             ),
             timeout=timeout,
         )
@@ -94,8 +98,8 @@ async def dispatch(req: DispatchRequest, request: Request):
 
     return DispatchResponse(
         directive_id=response.directive_id,
-        reply=response.reply,
-        agent_reports=[r.dict() if hasattr(r, 'dict') else r for r in response.agent_reports],
+        reply=response.response,
+        agent_reports=[],
         escalations=response.escalations,
         actions_taken=response.actions_taken,
         session_id=req.session_id,