feat(vm): IHost.Sleep seam + dispatch 0xc8 (headless hosts no-op; parity held)

- IHost.Sleep(long duration); VM case "sleep" forwards the raw operand.
- 8 non-Godot hosts no-op Sleep; RecordingHost records it.
- SleepDispatchTests (51 green); sweep unchanged 284 exit / 13 STEP-LIMIT.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

engine/Age.Engine.Tests/GameSessionTests.cs.bak

@@ -0,0 +1,132 @@
+using System.Collections.Generic;
+using System.Linq;
+using Age.Engine.Hosting;
+using Age.Engine.Model;
+using Age.Engine.Sys4;
+using Age.Engine.Vm;
+using Xunit;
+
+public class GameSessionTests
+{
+    private const int T_IMM = 0, T_GINT = 3;
+    private static readonly OpcodeTable Table = OpcodeTableJson.Load(Paths.OpcodesJson);
+
+    // A minimal one-instruction script: `mov (global-int dst) src`. Halts pc-out-of-range after.
+    private static Script MovScript(int dst, int srcType, long srcVal) => new()
+    {
+        Header = new ScriptHeader(0, 0, 0, 0, 0, 0),
+        Instructions = new[]
+        {
+            new Instruction(0, 0x55, new[] { new Operand(T_GINT, dst), new Operand(srcType, srcVal) }),
+        },
+        IndexByOffset = new Dictionary<int, int> { { 0, 0 } },
+        Strings = new Dictionary<int, string>(),
+    };
+
+    private sealed class VoiceCountHost : IHost
+    {
+        public int Voices;
+        public List<int> Emitted = new();
+        public void ShowText(int o, string t) => Emitted.Add(o);
+        public void WaitForInput() { }
+        public void CreateTexture(int s, int w, int h) { }
+        public void SetTexture(long r, int s) { }
+        public void DrawTexture(int s, int sx, int sy, int w, int h, int dx, int dy) { }
+        public (int Width, int Height) GetTextureSize(int slot) => (0, 0);
+        public void PlayBgm(long id) { }
+        public void PlayVoice(long id) => Voices++;
+    }
+
+    [Fact]
+    public void StatePersistsAcrossScenes()
+    {
+        var session = new GameSession();
+        // Scene A writes G[0x5000] = 42.
+        session.RunScene(MovScript(0x5000, T_IMM, 0x2a), Table, new CaptureHost());
+        Assert.Equal(0x2a, session.Globals[0x5000]);
+        // Scene B copies G[0x5000] -> G[0x5001]; it must SEE A's write.
+        session.RunScene(MovScript(0x5001, T_GINT, 0x5000), Table, new CaptureHost());
+        Assert.Equal(0x2a, session.Globals[0x5001]);
+    }
+
+    [Fact]
+    public void SeedIsVisibleToTheScene()
+    {
+        var session = new GameSession();
+        session.Seed(0x5000, 99);
+        session.RunScene(MovScript(0x5001, T_GINT, 0x5000), Table, new CaptureHost());
+        Assert.Equal(99, session.Globals[0x5001]);
+    }
+
+    [Fact]
+    public void SC0000ViaSessionMatchesSingleRun()
+    {
+        var script = Sys4Loader.Load(Paths.Scripts()["SC0000.BIN"], Table);
+        // single run
+        var host1 = new CaptureHost();
+        new VirtualMachine(script, Table, host1).Run();
+        var single = host1.Emitted.Select(e => e.Offset).ToList();
+        // via session
+        var host2 = new CaptureHost();
+        var r = new GameSession().RunScene(Sys4Loader.Load(Paths.Scripts()["SC0000.BIN"], Table), Table, host2);
+        var viaSession = r.Emitted.Select(e => e.Offset).ToList();
+        Assert.Equal(single, viaSession);
+        Assert.Equal("exit", r.Halt);
+    }
+
+    [Fact]
+    public void BootingSkinitPopulatesDataTableGlobals()
+    {
+        // Running the SKINIT data script through the session populates the real skill table into the
+        // global bank (the game's boot behavior). Cross-check vs the static extraction (build/data/SKINIT.json):
+        // skill 0 = "飛行" at global-string 0x23a3, field G[0xa6e5b] = 30.
+        var session = new GameSession();
+        var r = session.RunScene(Sys4Loader.Load(Paths.Scripts()["SKINIT.BIN"], Table), Table, new CaptureHost());
+        Assert.Equal("exit", r.Halt);
+        Assert.Equal("飛行", session.GlobalStrings[0x23a3]);
+        Assert.Equal(30, session.Globals[0xa6e5b]);
+        Assert.True(session.Globals.Count > 1000, $"SKINIT should populate the skill table (got {session.Globals.Count})");
+    }
+
+    [Fact]
+    public void SnapshotRoundTripsState()
+    {
+        var s = new GameSession();
+        s.Seed(0x10, 42); s.Seed(0x20, -7); s.SeedString(0x30, "リリィ");
+        var t = GameSession.FromJson(s.ToJson());
+        Assert.Equal(42, t.Globals[0x10]);
+        Assert.Equal(-7, t.Globals[0x20]);
+        Assert.Equal("リリィ", t.GlobalStrings[0x30]);
+        Assert.Equal(s.Globals.Count, t.Globals.Count);
+    }
+
+    [Fact]
+    public void BootedStateSurvivesSnapshot()
+    {
+        var s = new GameSession();
+        s.RunScene(Sys4Loader.Load(Paths.Scripts()["SKINIT.BIN"], Table), Table, new CaptureHost());
+        var t = GameSession.FromJson(s.ToJson());   // snapshot the expensive booted state, rebuild
+        Assert.Equal("飛行", t.GlobalStrings[0x23a3]);
+        Assert.Equal(30, t.Globals[0xa6e5b]);
+        Assert.Equal(s.Globals.Count, t.Globals.Count);
+        Assert.Equal(s.GlobalStrings.Count, t.GlobalStrings.Count);
+    }
+
+    [Fact]
+    public void SeedingFormFlagChangesBehavior()
+    {
+        // Lily's lines are gated on form flags G[0xa57/8/9]; unseeded => all skipped (0 voices on her lines).
+        // Seeding form A (0xa57=1) makes her lines execute -> more play-voice calls. Proven finding (audio).
+        var scriptPath = Paths.Scripts()["SC0000.BIN"];
+        var unseeded = new VoiceCountHost();
+        new GameSession().RunScene(Sys4Loader.Load(scriptPath, Table), Table, unseeded);
+
+        var s = new GameSession();
+        s.Seed(0xa57, 1);
+        var seeded = new VoiceCountHost();
+        s.RunScene(Sys4Loader.Load(scriptPath, Table), Table, seeded);
+
+        Assert.True(seeded.Voices > unseeded.Voices,
+            $"seeding form flag should fire more voices: unseeded={unseeded.Voices} seeded={seeded.Voices}");
+    }
+}