Move movie transition request to model

engine/Age.Engine/Model/MovieMaskTransitionRequest.cs

@@ -0,0 +1,8 @@
+namespace Age.Engine.Model;
+
+/// <summary>Opcode 0x24d's captured-range movie-mask transition. The movie's decoded green channel
+/// becomes a byte-per-pixel alpha mask over SourceRange in the scratch surface.</summary>
+public readonly record struct MovieMaskTransitionRequest(
+    long CommandKey, int SurfaceSlot, long SourceRangeStart, int SourceRangeCount,
+    int X, int Y, int Width, int Height, long Mode, long ResourceId,
+    long StartDelayMs, long DurationMs);