feat(chargen): Campaign CC slice CC6a — index→ObjDesc factory + preview renderer foundation

Delivers the CC6a foundation half of the chargen 3D preview: the missing
index->ObjDesc appearance factory the campaign plan's acdream-seams
section named, plus a static-pose offscreen renderer following
PrivateEntityViewportRenderer's proven paperdoll/appraisal architecture.
Page mount, spin/color-wheel controls, and rotate/zoom behavior stay out
of scope per the CC4-parallel worktree contract (CC6b, after CC4 merges).

Core (src/AcDream.Core/CharGen/, pure, no Chorizite on public surfaces):
ChargenAppearanceFactory.TryCompose ports gmCG3DView::Update @0x004EE9D0's
ObjDesc rebuild in its exact decompiled order - base body, hair style,
clothing in retail's own Headgear/Trousers/Shirt/Footwear order (not the
UI tab order or the wire's field order, both of which differ), eyes
(bald-aware), nose, mouth, then the unconditional skin subpalette, hair
color, eye color. ChargenPalSetMath ports PalSet::GetPaletteID's
shade-to-index formula, cross-checked three ways (decomp control flow,
ACE's PaletteSet.GetPaletteID "Taken from acclient.c" citation, ACViewer's
identical slider math). ChargenPalSet/ChargenClothingTable are pure
projections behind IChargenPalSetSource/IChargenClothingTableSource so the
factory itself never touches a dat.

Content (src/AcDream.Content/CharGen/): ChargenAppearanceCatalog is the
cached dat-backed implementation of those two source interfaces, mirroring
ChargenTableReader's no-leak discipline.

App (src/AcDream.App/Rendering/): ChargenPreviewRenderer is a third facade
over PrivateEntityViewportRenderer beside PaperdollViewportRenderer and
CreatureAppraisalViewportRenderer - no existing rendering file touched.
ChargenPreviewCamera carries the four retail-verbatim per-heritage eye
profiles from gmCGAppearancePage::Update @0x0047E8F0 (cross-checked
against ZoomIn/ZoomOut's identical literals) plus the recovered rotation
(3.0 s/revolution) and zoom-tween (0.6 s, reconstructed from the
decompiler's garbled float literals - the plan's own "measure if it
matters" note is resolved, not garbled beyond recovery). Rotation applies
to the character model, not the camera, per gmCGAppearancePage::DoRotation.
ChargenPreviewEntityBuilder resolves Setup/GfxObj/Surface/Animation itself
(there is no live entity yet), reusing DatLiveEntityProjectionMaterializer's
surface-override algorithm and RetailPaperdollPoseApplicator's held-pose
technique, generalized to chargen's per-heritage rest-pose DID.

Two register rows filed: TS-83 (the plan-named CC6a static-pose-vs-retail-
idle-loop staging, CC6b to retire) and TS-82 (measured, not assumed - the
un-ported clothing Setup-substitution fallback chain costs nothing for the
9 standard heritages with clothing UI, but Undead's default gear choices
genuinely lack ClothingBaseEffects coverage for Undead's own body Setup).

Tests: ChargenPalSetMathTests, ChargenAppearanceFactoryTests (hand-built
fixtures), ChargenAppearanceCatalogInstalledDatTests (installed-DAT sweep,
all 26 heritage/gender combinations, zero missing PalSet/ClothingTable
ids), ChargenPreviewCameraTests, ChargenPreviewEntityBuilderTests
(installed-DAT-gated, proves a real 34-part Aluvian mesh resolves).
Core.Tests 4767/1 skip, Content.Tests 146/0, App.Tests 5121/6 skips - all
pre-existing skips, zero failures, full solution Release build green.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

tests/AcDream.Core.Tests/CharGen/ChargenPalSetMathTests.cs

@@ -0,0 +1,63 @@
+using AcDream.Core.CharGen;
+
+namespace AcDream.Core.Tests.CharGen;
+
+/// <summary>
+/// Pins <see cref="ChargenPalSetMath.GetPaletteIndex"/> against the exact
+/// formula ACE's <c>PaletteSet.GetPaletteID</c> cites as "Taken from
+/// acclient.c (PalSet::GetPaletteID)": <c>(int)((count - 0.000001) * shade)</c>,
+/// clamped to <c>[0, count-1]</c>, with an out-of-<c>[0,1]</c> shade (or a
+/// non-positive count) returning -1.
+/// </summary>
+public class ChargenPalSetMathTests
+{
+    [Theory]
+    [InlineData(5, 0.0, 0)]
+    [InlineData(5, 1.0, 4)]
+    [InlineData(5, 0.5, 2)]
+    [InlineData(1, 0.0, 0)]
+    [InlineData(1, 1.0, 0)]
+    public void GetPaletteIndex_matches_the_cited_acclient_formula(int count, double shade, int expected)
+    {
+        Assert.Equal(expected, ChargenPalSetMath.GetPaletteIndex(count, shade));
+    }
+
+    [Theory]
+    [InlineData(0, 0.5)]
+    [InlineData(-1, 0.5)]
+    public void GetPaletteIndex_returns_negative_one_for_non_positive_count(int count, double shade)
+    {
+        Assert.Equal(-1, ChargenPalSetMath.GetPaletteIndex(count, shade));
+    }
+
+    [Theory]
+    [InlineData(5, -0.0001)]
+    [InlineData(5, 1.0001)]
+    [InlineData(5, ChargenAppearanceSelection.UnsetShade)] // retail's own "unset" sentinel is out of [0,1].
+    public void GetPaletteIndex_returns_negative_one_for_out_of_range_shade(int count, double shade)
+    {
+        Assert.Equal(-1, ChargenPalSetMath.GetPaletteIndex(count, shade));
+    }
+
+    [Fact]
+    public void GetPaletteIndex_never_exceeds_count_minus_one_near_the_upper_bound()
+    {
+        // shade == 1.0 exactly must land on the LAST index, not overflow past it —
+        // the (count - 0.000001) fudge factor exists precisely to guarantee this.
+        for (int count = 1; count <= 64; count++)
+            Assert.Equal(count - 1, ChargenPalSetMath.GetPaletteIndex(count, 1.0));
+    }
+
+    [Fact]
+    public void GetPaletteIndex_is_monotonic_non_decreasing_in_shade()
+    {
+        const int count = 13;
+        int previous = -1;
+        for (double shade = 0.0; shade <= 1.0; shade += 0.01)
+        {
+            int index = ChargenPalSetMath.GetPaletteIndex(count, shade);
+            Assert.True(index >= previous, $"index regressed at shade={shade}");
+            previous = index;
+        }
+    }
+}