phase(N.4) Tasks 16+18+19: AnimatedEntityState + AnimPartChange + HiddenParts

Per-entity render state for the per-instance rendering tier
(server-spawned characters / creatures / equipped items). Holds:
- partGfxObjOverrides: Dictionary<int, ulong> — AnimPartChange swaps
  (e.g. wielding a weapon replaces a hand-part's GfxObj).
- hiddenMask: ulong — HiddenParts bitmask. Bit i set hides part i.
- AnimationSequencer reference — N.4 doesn't touch the sequencer;
  this just exposes it for the draw dispatcher.

Public API: HideParts / IsPartHidden / SetPartOverride /
TryGetPartOverride / ResolvePartGfxObj. Bounds-checked
(partIdx < 0 or >= 64 → IsPartHidden returns false).

Twelve tests covering the type, the AnimPartChange resolution helper,
and the HiddenParts bitmask edge cases (theories for 0b0/0b1/MSB/all-ones,
plus negative-index + out-of-range guards).

Consumed by Task 17's EntitySpawnAdapter (creates one per CreateObject)
and Task 22's WbDrawDispatcher (reads via per-part draw loop).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

tests/AcDream.Core.Tests/Rendering/Wb/AnimPartChangeTests.cs

@@ -0,0 +1,62 @@
+using AcDream.App.Rendering.Wb;
+using AcDream.Core.Physics;
+using DatReaderWriter.DBObjs;
+using Xunit;
+
+namespace AcDream.Core.Tests.Rendering.Wb;
+
+public sealed class AnimPartChangeTests
+{
+    [Fact]
+    public void SetPartOverride_ResolvedAtLookup()
+    {
+        var state = MakeState();
+
+        state.SetPartOverride(partIdx: 5, gfxObjId: 0x01001234ul);
+
+        Assert.True(state.TryGetPartOverride(5, out var got));
+        Assert.Equal(0x01001234ul, got);
+        Assert.False(state.TryGetPartOverride(6, out _));
+    }
+
+    [Fact]
+    public void SetPartOverride_TwiceForSamePart_TakesLatest()
+    {
+        var state = MakeState();
+
+        state.SetPartOverride(0, 0x01000001ul);
+        state.SetPartOverride(0, 0x01999999ul);
+
+        Assert.True(state.TryGetPartOverride(0, out var got));
+        Assert.Equal(0x01999999ul, got);
+    }
+
+    [Fact]
+    public void ResolvePartGfxObj_WithoutOverride_ReturnsSetupDefault()
+    {
+        var state = MakeState();
+
+        Assert.Equal(0x01000001ul,
+            state.ResolvePartGfxObj(partIdx: 0, setupDefault: 0x01000001ul));
+    }
+
+    [Fact]
+    public void ResolvePartGfxObj_WithOverride_ReturnsOverride()
+    {
+        var state = MakeState();
+        state.SetPartOverride(partIdx: 0, gfxObjId: 0x01999999ul);
+
+        Assert.Equal(0x01999999ul,
+            state.ResolvePartGfxObj(partIdx: 0, setupDefault: 0x01000001ul));
+    }
+
+    private static AnimatedEntityState MakeState() => new(MakeSequencer());
+
+    private static AnimationSequencer MakeSequencer()
+        => new AnimationSequencer(new Setup(), new MotionTable(), new NullAnimationLoader());
+
+    private sealed class NullAnimationLoader : IAnimationLoader
+    {
+        public Animation? LoadAnimation(uint id) => null;
+    }
+}

tests/AcDream.Core.Tests/Rendering/Wb/AnimatedEntityStateTests.cs

@@ -0,0 +1,45 @@
+using AcDream.App.Rendering.Wb;
+using AcDream.Core.Physics;
+using DatReaderWriter.DBObjs;
+using Xunit;
+
+namespace AcDream.Core.Tests.Rendering.Wb;
+
+public sealed class AnimatedEntityStateTests
+{
+    [Fact]
+    public void DefaultState_HasNoOverridesAndNoHiddenParts()
+    {
+        var state = MakeState();
+
+        Assert.False(state.IsPartHidden(0));
+        Assert.False(state.IsPartHidden(63));
+        Assert.False(state.TryGetPartOverride(0, out _));
+    }
+
+    [Fact]
+    public void Sequencer_AccessibleAsProperty()
+    {
+        var sequencer = MakeSequencer();
+        var state = new AnimatedEntityState(sequencer);
+
+        Assert.Same(sequencer, state.Sequencer);
+    }
+
+    [Fact]
+    public void Construct_WithNullSequencer_ThrowsArgumentNull()
+    {
+        Assert.Throws<System.ArgumentNullException>(
+            () => new AnimatedEntityState(null!));
+    }
+
+    private static AnimatedEntityState MakeState() => new(MakeSequencer());
+
+    private static AnimationSequencer MakeSequencer()
+        => new AnimationSequencer(new Setup(), new MotionTable(), new NullAnimationLoader());
+
+    private sealed class NullAnimationLoader : IAnimationLoader
+    {
+        public Animation? LoadAnimation(uint id) => null;
+    }
+}

tests/AcDream.Core.Tests/Rendering/Wb/HiddenPartsTests.cs

@@ -0,0 +1,56 @@
+using AcDream.App.Rendering.Wb;
+using AcDream.Core.Physics;
+using DatReaderWriter.DBObjs;
+using Xunit;
+
+namespace AcDream.Core.Tests.Rendering.Wb;
+
+public sealed class HiddenPartsTests
+{
+    [Theory]
+    [InlineData(0b0000_0000ul, 0, false)]
+    [InlineData(0b0000_0001ul, 0, true)]
+    [InlineData(0b1000_0000ul, 7, true)]
+    [InlineData(0b1000_0000ul, 6, false)]
+    [InlineData(0xFFFF_FFFF_FFFF_FFFFul, 63, true)]
+    public void IsPartHidden_RespectsBitmaskBit(ulong mask, int partIdx, bool expected)
+    {
+        var state = MakeState();
+        state.HideParts(mask);
+        Assert.Equal(expected, state.IsPartHidden(partIdx));
+    }
+
+    [Fact]
+    public void IsPartHidden_NegativeIdx_ReturnsFalse()
+    {
+        var state = MakeState();
+        state.HideParts(0xFFFF_FFFF_FFFF_FFFFul);
+        Assert.False(state.IsPartHidden(-1));
+    }
+
+    [Fact]
+    public void IsPartHidden_PartIdxOver64_ReturnsFalse()
+    {
+        var state = MakeState();
+        state.HideParts(0xFFFF_FFFF_FFFF_FFFFul);
+        Assert.False(state.IsPartHidden(64));
+    }
+
+    [Fact]
+    public void HideParts_DefaultsToNoneHidden()
+    {
+        var state = MakeState();
+        for (int i = 0; i < 64; i++)
+            Assert.False(state.IsPartHidden(i));
+    }
+
+    private static AnimatedEntityState MakeState() => new(MakeSequencer());
+
+    private static AnimationSequencer MakeSequencer()
+        => new AnimationSequencer(new Setup(), new MotionTable(), new NullAnimationLoader());
+
+    private sealed class NullAnimationLoader : IAnimationLoader
+    {
+        public Animation? LoadAnimation(uint id) => null;
+    }
+}