fix: guard reply_to_text against DeletedReferencedMessage

Use getattr() for resolved.content since discord.py's
DeletedReferencedMessage lacks a content attribute. Adds test
for the deleted-message edge case.

gateway/platforms/discord.py

@@ -2480,7 +2480,7 @@ class DiscordAdapter(BasePlatformAdapter):
         if message.reference:
             reply_to_id = str(message.reference.message_id)
             if message.reference.resolved:
-                reply_to_text = message.reference.resolved.content or None
+                reply_to_text = getattr(message.reference.resolved, "content", None) or None
 
         event = MessageEvent(
             text=event_text,

tests/gateway/test_discord_reply_mode.py

@@ -369,3 +369,16 @@ class TestReplyToText:
         event = reply_text_adapter.handle_message.await_args.args[0]
         assert event.reply_to_message_id == "555"
         assert event.reply_to_text is None
+
+    @pytest.mark.asyncio
+    async def test_reference_with_deleted_message(self, reply_text_adapter):
+        """Deleted messages lack .content — getattr guard should return None."""
+        resolved_deleted = SimpleNamespace(id=555)
+        ref = SimpleNamespace(message_id=555, resolved=resolved_deleted)
+        message = _make_message(reference=ref)
+
+        await reply_text_adapter._handle_message(message)
+
+        event = reply_text_adapter.handle_message.await_args.args[0]
+        assert event.reply_to_message_id == "555"
+        assert event.reply_to_text is None