fix(matrix): reconcile pending invites from sync state

tests/gateway/test_matrix.py

@@ -1204,6 +1204,40 @@ class TestMatrixSyncLoop:
         fake_client.handle_sync.assert_called_once()
         mock_sync_store.put_next_batch.assert_awaited_once_with("s1234")
 
+    @pytest.mark.asyncio
+    async def test_sync_loop_reconciles_pending_invites(self):
+        """Pending rooms.invite entries should be joined if callbacks were missed."""
+        adapter = _make_adapter()
+        adapter._closing = False
+
+        async def _sync_once(**kwargs):
+            adapter._closing = True
+            return {
+                "rooms": {
+                    "join": {"!joined:example.org": {}},
+                    "invite": {"!invited:example.org": {}},
+                },
+                "next_batch": "s1234",
+            }
+
+        mock_sync_store = MagicMock()
+        mock_sync_store.get_next_batch = AsyncMock(return_value=None)
+        mock_sync_store.put_next_batch = AsyncMock()
+
+        fake_client = MagicMock()
+        fake_client.sync = AsyncMock(side_effect=_sync_once)
+        fake_client.join_room = AsyncMock()
+        fake_client.sync_store = mock_sync_store
+        fake_client.handle_sync = MagicMock(return_value=[])
+        adapter._client = fake_client
+
+        with patch.object(adapter, "_refresh_dm_cache", AsyncMock()):
+            await adapter._sync_loop()
+
+        fake_client.join_room.assert_awaited_once()
+        assert "!joined:example.org" in adapter._joined_rooms
+        assert "!invited:example.org" in adapter._joined_rooms
+
 
 class TestMatrixUploadAndSend:
     @pytest.mark.asyncio