feat: standalone .ly interpreter - parses blocks/wires, executes flow control

Engine/VisualScript/block_executor.h

@@ -68,3 +68,7 @@ void executor_update(BlockExecutor* exec, double delta_time);
 void executor_set_variable(BlockExecutor* exec, const char* name, SlotValue value);
 SlotValue executor_get_variable(BlockExecutor* exec, const char* name);
 void executor_create_variable(BlockExecutor* exec, const char* name);
+
+// 日志回调
+typedef void (*LogCallback)(const char* msg, int level);
+void executor_set_log_callback(LogCallback cb);