Implement ROOM fades and character voices

engine/Age.Engine/Model/LegacyScreenTransitionTiming.cs

@@ -0,0 +1,13 @@
+namespace Age.Engine.Model;
+
+/// <summary>Native timing conversion shared by the legacy op-0x25 screen-transition family.</summary>
+public static class LegacyScreenTransitionTiming
+{
+    public static long DurationMilliseconds(long argument)
+    {
+        long interval = argument <= 64 ? argument : argument / 16;
+        long step = argument <= 64 ? 16 : 1;
+        interval = System.Math.Max(1, interval);
+        return System.Math.Clamp(((256 + step - 1) / step) * interval, 1, 60_000);
+    }
+}