fix(bridge): 5 bug fixes for approval signal drop and Discord relay

- DEDUP: add conversation_id guard to prevent cross-session step_index collision
- step_probe: suppress pending when projectName=default (empty window)
- watchCommandsDir: add 3s polling fallback (fs.watch silent fail on Windows)
- auto toggle: write chat_snapshot confirmation back to Discord
- bot on_message: add message ID dedup for Gateway event replay

bot.py

@@ -180,6 +180,7 @@ class GravityBot(commands.Bot):
         self.session_category: discord.CategoryChannel | None = None
         self.guild: discord.Guild | None = None
         self.auto_approve_projects: set[str] = set()  # projects with auto-approve enabled
+        self._processed_message_ids: set[int] = set()  # dedup for Gateway event replay
         self.gateway = None  # Set by main.py in gateway mode
 
     def _write_command(self, project: str, text: str, **kwargs):
@@ -771,6 +772,16 @@ class GravityBot(commands.Bot):
         if message.author == self.user:
             return
 
+        # Dedup: Discord Gateway can deliver MESSAGE_CREATE twice on reconnection
+        if message.id in self._processed_message_ids:
+            return
+        self._processed_message_ids.add(message.id)
+        # Keep set bounded (last 200 messages)
+        if len(self._processed_message_ids) > 200:
+            excess = len(self._processed_message_ids) - 100
+            for _ in range(excess):
+                self._processed_message_ids.pop()
+
         # Determine project from channel
         project = self.channel_to_project.get(message.channel.id)
         if not project: