feat: classify mention intent before running expensive scan

Adds LLM triage on bot @mentions to determine if the user is chatting
or reporting bad behavior. Only 'report' intents trigger the 30-message
scan; 'chat' intents skip the scan and let ChatCog handle it.

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

cogs/sentiment/__init__.py

@@ -103,9 +103,18 @@ class SentimentCog(commands.Cog):
             or f"<@!{self.bot.user.id}>" in (message.content or "")
         )
         if bot_mentioned_in_text:
-            mention_config = config.get("mention_scan", {})
-            if mention_config.get("enabled", True):
-                await self._maybe_start_mention_scan(message, mention_config)
+            # Classify intent: only run expensive mention scan for reports,
+            # let ChatCog handle casual chat/questions
+            intent = await self.bot.llm.classify_mention_intent(
+                message.content or ""
+            )
+            logger.info(
+                "Mention intent for %s: %s", message.author, intent
+            )
+            if intent == "report":
+                mention_config = config.get("mention_scan", {})
+                if mention_config.get("enabled", True):
+                    await self._maybe_start_mention_scan(message, mention_config)
             return
 
         # Skip if empty