fix(backend/orchestrator): use AsyncMock for charge_node_usage in test

charge_node_usage is async and is directly awaited; using MagicMock
caused a TypeError that was silently swallowed by the outer except
Exception block, meaning the billing assertion passed for the wrong
reason (mock called but await failed, so no billing actually ran).

autogpt_platform/backend/backend/blocks/test/test_orchestrator.py

@@ -923,10 +923,10 @@ async def test_orchestrator_agent_mode():
             return_value=mock_node_stats
         )
         # Mock charge_node_usage (called after successful tool execution).
-        # Returns (cost, remaining_balance). Synchronous because it's called
-        # via asyncio.to_thread. Use a non-zero cost so the merge_stats
-        # branch is actually exercised, and assert it's called below.
-        mock_execution_processor.charge_node_usage = MagicMock(return_value=(10, 990))
+        # Returns (cost, remaining_balance). Must be AsyncMock because it is
+        # an async method and is directly awaited in _execute_single_tool_with_manager.
+        # Use a non-zero cost so the merge_stats branch is exercised.
+        mock_execution_processor.charge_node_usage = AsyncMock(return_value=(10, 990))
 
         # Mock the get_execution_outputs_by_node_exec_id method
         mock_db_client.get_execution_outputs_by_node_exec_id.return_value = {