Fix proactive replies appearing before the triggering message

Proactive replies used channel.send() which posted standalone messages
with no visual link to what triggered them. Now all replies use
message.reply() so the response is always attached to the source message.

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

cogs/chat.py

@@ -221,10 +221,7 @@ class ChatCog(commands.Cog):
                 except (asyncio.TimeoutError, asyncio.CancelledError):
                     pass
 
-        if is_proactive:
-            await message.channel.send(response)
-        else:
-            await message.reply(response, mention_author=False)
+        await message.reply(response, mention_author=False)
 
         reply_type = "proactive" if is_proactive else "chat"
         logger.info(