Add switchable bot modes: default, chatty, and roast

Adds a server-wide mode system with /bcs-mode command.
- Default: current hall-monitor behavior unchanged
- Chatty: friendly chat participant with proactive replies (~10% chance)
- Roast: savage roast mode with proactive replies
- Chatty/roast use relaxed moderation thresholds
- 5-message cooldown between proactive replies per channel
- Bot status updates to reflect active mode
- /bcs-status shows current mode and effective thresholds

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

bot.py

@@ -78,6 +78,10 @@ class BCSBot(commands.Bot):
         llm_heavy_model = os.getenv("LLM_ESCALATION_MODEL", llm_model)
         self.llm_heavy = LLMClient(llm_base_url, llm_heavy_model, llm_api_key, db=self.db)
 
+        # Active mode (server-wide)
+        modes_config = config.get("modes", {})
+        self.current_mode = modes_config.get("default_mode", "default")
+
         # Drama tracker
         sentiment = config.get("sentiment", {})
         timeouts = config.get("timeouts", {})
@@ -87,6 +91,11 @@ class BCSBot(commands.Bot):
             offense_reset_minutes=timeouts.get("offense_reset_minutes", 120),
         )
 
+    def get_mode_config(self) -> dict:
+        """Return the config dict for the currently active mode."""
+        modes = self.config.get("modes", {})
+        return modes.get(self.current_mode, modes.get("default", {}))
+
     async def setup_hook(self):
         # Initialize database and hydrate DramaTracker
         db_ok = await self.db.init()