unstub: preserve notice screen skip flag (#559)

* fix(system-service): preserve notice screen skip flag

* test(bink): avoid frame timing flake on CI

tests/SharpEmu.Libs.Tests/Bink/BinkFramePlaybackTests.cs

@@ -83,7 +83,9 @@ public sealed class BinkFramePlaybackTests
 
         public uint Height => 1;
 
-        public uint FramesPerSecondNumerator => 20;
+        // Keep frame boundaries far enough apart that a loaded CI runner cannot
+        // skip an expected frame between polling iterations.
+        public uint FramesPerSecondNumerator => 2;
 
         public uint FramesPerSecondDenominator => 1;
 

tests/SharpEmu.Libs.Tests/SystemService/SystemServiceExportsTests.cs

@@ -11,6 +11,11 @@ public sealed class SystemServiceExportsTests
 {
     private const ulong MemoryBase = 0x1_0000_0000;
 
+    public SystemServiceExportsTests()
+    {
+        SystemServiceExports.ResetForTests();
+    }
+
     [Fact]
     public void GetNoticeScreenSkipFlagWritesOneByteAtMemoryBoundary()
     {
@@ -26,4 +31,23 @@ public sealed class SystemServiceExportsTests
         Assert.True(memory.TryRead(MemoryBase, flag));
         Assert.Equal(0, flag[0]);
     }
+
+    [Fact]
+    public void SetNoticeScreenSkipFlagRoundTripsThroughGetter()
+    {
+        var memory = new FakeCpuMemory(MemoryBase, 2);
+        var context = new CpuContext(memory, Generation.Gen5)
+        {
+            [CpuRegister.Rdi] = 1,
+        };
+
+        Assert.Equal(0, SystemServiceExports.SystemServiceSetNoticeScreenSkipFlag(context));
+
+        context[CpuRegister.Rdi] = MemoryBase;
+        Assert.Equal(0, SystemServiceExports.SystemServiceGetNoticeScreenSkipFlag(context));
+
+        Span<byte> flag = stackalloc byte[1];
+        Assert.True(memory.TryRead(MemoryBase, flag));
+        Assert.Equal(1, flag[0]);
+    }
 }