Fix slixmpp 1.13 compatibility and empty capabilities handling

- Replace process(forever=True) with asyncio event loop in _SlixClient.start()
- Make send_xmpp_message() thread-safe via loop.call_soon_threadsafe()
- Remove wait=True from join_muc() (no longer supported in slixmpp 1.13)
- Silence empty retained MQTT capability messages in CapabilitiesRegistry

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

agents_core/capabilities.py

@@ -63,6 +63,8 @@ class CapabilitiesRegistry:
         logger.debug(f"[Registry] Capacités mises à jour pour {caps.agent_id}")
 
     def update_from_json(self, data: str | bytes) -> Optional[AgentCapabilities]:
+        if not data or (isinstance(data, (str, bytes)) and not data.strip()):
+            return None  # Empty retained message — ignore silently
         try:
             caps = AgentCapabilities.from_json(data)
             self.update(caps)

agents_core/xmpp_client.py

@@ -187,8 +187,12 @@ class _SlixClient(ClientXMPP):
             logger.warning(f"[XMPP] OMEMO non disponible : {e}")
 
     def start(self):
+        import asyncio
+        loop = asyncio.new_event_loop()
+        asyncio.set_event_loop(loop)
+        self.loop = loop
         self.connect()
-        self.process(forever=True)
+        loop.run_forever()
 
     async def _on_session_start(self, event):
         self.send_presence()
@@ -197,7 +201,6 @@ class _SlixClient(ClientXMPP):
             self.plugin["xep_0045"].join_muc(
                 room=self._muc_room,
                 nick=self._muc_nick,
-                wait=True,
             )
         if self._on_connected_cb:
             self._on_connected_cb()
@@ -217,5 +220,10 @@ class _SlixClient(ClientXMPP):
                 self._on_message_cb(str(msg["from"]), body, is_muc=True)
 
     def send_xmpp_message(self, to: str, body: str, is_muc: bool = False):
+        import functools
         msg_type = "groupchat" if is_muc else "chat"
-        self.send_message(mto=to, mbody=body, mtype=msg_type)
+        fn = functools.partial(self.send_message, mto=to, mbody=body, mtype=msg_type)
+        if hasattr(self, 'loop') and self.loop and self.loop.is_running():
+            self.loop.call_soon_threadsafe(fn)
+        else:
+            fn()