fix(rendering): #47 — walk DIDDegrade for retail close-detail meshes

Humanoid bodies (Setup 0x02000001 + heritage variants) rendered visibly
flat / bulky vs retail because we drew the base GfxObj id from Setup /
AnimPartChange directly. Retail's CPhysicsPart::LoadGfxObjArray
(0x0050DCF0) treats that base id as the entry point to a DIDDegrade
table; close/player rendering uses Degrades[0].Id, which is the
higher-detail mesh that carries bicep / deltoid / shoulder geometry.

ACViewer also has this bug — it was the key signal it isn't acdream-
specific. Both clients drew the LOD-3 base mesh (e.g. 14 verts / 17
polys for Aluvian Male upper arm 0x01000055), missing the close-
detail variant (0x01001795: 32 verts / 60 polys).

Adds GfxObjDegradeResolver that walks the table with safe fallbacks
at every step. Wired in GameWindow after AnimPartChange application
and before texture-change resolution so texture overrides match the
resolved mesh's surfaces. Gated by ACDREAM_RETAIL_CLOSE_DEGRADES=1
and scoped to humanoid setups (34 parts with >=8 null-sentinel
attachment slots) while the fix bakes — the change is harmless on
non-humanoid setups (resolver falls back to base when no degrade
table) but we hold the broader sweep until LOD distance plumbing
lands.

User confirmed visually 2026-05-06: bicep, deltoid, and back-muscle
definition match retail.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/AcDream.App/Rendering/GameWindow.cs

@@ -172,6 +172,38 @@ public sealed class GameWindow : IDisposable
     // Diagnostic: hide a specific humanoid part (>=10 parts) at render.
     private static readonly int s_hidePartIndex =
         int.TryParse(Environment.GetEnvironmentVariable("ACDREAM_HIDE_PART"), out var hp) ? hp : -1;
+
+    // Issue #47 — opt in to retail's close-detail GfxObj selection on
+    // humanoid setups. When enabled, every per-part GfxObj id (after
+    // server AnimPartChanges are applied) is replaced with Degrades[0]
+    // from its DIDDegrade table when present. See GfxObjDegradeResolver
+    // for the full retail-decomp citation. Off by default while the fix
+    // bakes; flip to default-on once we've confirmed no scenery/setup
+    // regressions.
+    private static readonly bool s_retailCloseDegrades =
+        string.Equals(Environment.GetEnvironmentVariable("ACDREAM_RETAIL_CLOSE_DEGRADES"), "1", StringComparison.Ordinal);
+
+    /// <summary>
+    /// Issue #47 humanoid-setup detector. Matches Aluvian Male
+    /// (<c>0x02000001</c>) and the 34-part heritage sibling setups
+    /// (Aluvian Female, Sho M/F, Gharu M/F, Viamont/Empyrean, etc.)
+    /// by structure rather than id list: a humanoid setup has exactly
+    /// 34 parts, and the trailing attachment slots (parts 17–33) are
+    /// the AC null-part sentinel <c>0x010001EC</c>. Non-humanoid
+    /// 34-part setups (rare) won't have the sentinel pattern.
+    /// </summary>
+    private static bool IsIssue47HumanoidSetup(DatReaderWriter.DBObjs.Setup setup)
+    {
+        if (setup.Parts.Count != 34) return false;
+        const uint NullPartGfx = 0x010001ECu;
+        int nullSlots = 0;
+        for (int i = 17; i < setup.Parts.Count; i++)
+            if ((uint)setup.Parts[i] == NullPartGfx) nullSlots++;
+        // At least half of slots 17–33 wired to the null sentinel — enough
+        // to distinguish humanoids from any future 34-part creature setup.
+        return nullSlots >= 8;
+    }
+
     private readonly HashSet<SkyPesKey> _activeSkyPes = new();
     private readonly HashSet<SkyPesKey> _missingSkyPes = new();
 
@@ -2076,6 +2108,41 @@ public sealed class GameWindow : IDisposable
             }
         }
 
+        // Issue #47 — retail's close/player rendering path resolves each
+        // part's base GfxObj through its DIDDegrade table to the close-
+        // detail mesh in slot 0. Without this, humanoid arms/torso draw
+        // the LOW-detail base GfxObj (e.g. 0x01000055, 14 verts / 17
+        // polys) instead of the close mesh (0x01001795, 32 verts / 60
+        // polys), losing all bicep/shoulder/back geometry. See
+        // <see cref="GfxObjDegradeResolver"/> for the named-retail
+        // citation (CPhysicsPart::LoadGfxObjArray at 0x0050DCF0,
+        // ::UpdateViewerDistance at 0x0050E030, ::Draw at 0x0050D7A0).
+        //
+        // Order matters: the swap happens AFTER AnimPartChanges have
+        // installed the server's body/clothing/head ids, BEFORE texture
+        // changes resolve (which match against the resolved mesh's
+        // surfaces) and BEFORE the GfxObjMesh.Build / texture upload
+        // path consumes the part list.
+        if (s_retailCloseDegrades && IsIssue47HumanoidSetup(setup))
+        {
+            for (int partIdx = 0; partIdx < parts.Count; partIdx++)
+            {
+                var part = parts[partIdx];
+                if (!AcDream.Core.Meshing.GfxObjDegradeResolver.TryResolveCloseGfxObj(
+                        _dats, part.GfxObjId,
+                        out uint resolvedId, out _))
+                    continue;
+                if (resolvedId == part.GfxObjId)
+                    continue;
+
+                parts[partIdx] = new AcDream.Core.World.MeshRef(
+                    resolvedId, part.PartTransform);
+
+                if (dumpClothing)
+                    Console.WriteLine($"  DEGRADE part={partIdx:D2} gfx=0x{part.GfxObjId:X8} -> close=0x{resolvedId:X8}");
+            }
+        }
+
         // Build per-part texture overrides. The server sends TextureChanges as
         // (partIdx, oldSurfaceTextureId, newSurfaceTextureId) where both ids
         // are in the SurfaceTexture (0x05) range. Our sub-meshes are keyed