add convert rules for struct

.cursor/rules/cpp-convert-rules.mdc

@@ -0,0 +1,13 @@
+---
+alwaysApply: true
+---
+When convert cpp to c#
+- unsigned long convert to uint
+- unsigned char to byte
+- task_char to ushort
+- Keeps all the naming
+- keeps all the original chinese comments. But add a translated English version side by side
+- struct has to be public 
+- struct has to be use [StructLayout(LayoutKind.Sequential, Pack = 1)] 
+- all field in struct has to be public 
+- array has to be use [MarshalAs(UnmanagedType.ByValArray, SizeConst = )] to fix the array size