fix: remove dead pub/sub code from MessageBus

`subscribe_outbound()`, `dispatch_outbound()`, and `stop()` have zero
callers — `ChannelManager._dispatch_outbound()` handles all outbound
routing via `consume_outbound()` directly. Remove the dead methods and
their unused imports (`Callable`, `Awaitable`, `logger`).

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

nanobot/bus/queue.py

@@ -1,9 +1,6 @@
 """Async message queue for decoupled channel-agent communication."""
 
 import asyncio
-from typing import Callable, Awaitable
-
-from loguru import logger
 
 from nanobot.bus.events import InboundMessage, OutboundMessage
 
@@ -19,8 +16,6 @@ class MessageBus:
     def __init__(self):
         self.inbound: asyncio.Queue[InboundMessage] = asyncio.Queue()
         self.outbound: asyncio.Queue[OutboundMessage] = asyncio.Queue()
-        self._outbound_subscribers: dict[str, list[Callable[[OutboundMessage], Awaitable[None]]]] = {}
-        self._running = False
 
     async def publish_inbound(self, msg: InboundMessage) -> None:
         """Publish a message from a channel to the agent."""
@@ -38,38 +33,6 @@ class MessageBus:
         """Consume the next outbound message (blocks until available)."""
         return await self.outbound.get()
 
-    def subscribe_outbound(
-        self, 
-        channel: str, 
-        callback: Callable[[OutboundMessage], Awaitable[None]]
-    ) -> None:
-        """Subscribe to outbound messages for a specific channel."""
-        if channel not in self._outbound_subscribers:
-            self._outbound_subscribers[channel] = []
-        self._outbound_subscribers[channel].append(callback)
-    
-    async def dispatch_outbound(self) -> None:
-        """
-        Dispatch outbound messages to subscribed channels.
-        Run this as a background task.
-        """
-        self._running = True
-        while self._running:
-            try:
-                msg = await asyncio.wait_for(self.outbound.get(), timeout=1.0)
-                subscribers = self._outbound_subscribers.get(msg.channel, [])
-                for callback in subscribers:
-                    try:
-                        await callback(msg)
-                    except Exception as e:
-                        logger.error(f"Error dispatching to {msg.channel}: {e}")
-            except asyncio.TimeoutError:
-                continue
-    
-    def stop(self) -> None:
-        """Stop the dispatcher loop."""
-        self._running = False
-    
     @property
     def inbound_size(self) -> int:
         """Number of pending inbound messages."""