fix #426: extract solid-colour (NO_POS_UVS) faces; skip untextured subsets only on building shells and cells like retail

The Holtburg windmill axle (GfxObj 0x010010CE, 8 polygons, all
Stippling.NoPos + SurfaceType.Base1Solid) extracted to a 0-vertex mesh.
NoPos ("NO_POS_UVS", acclient.h:7380-7388) means "this side has no
texture coordinates" — true of every solid-colour polygon, since
nothing samples them — not "there is no positive face". Extraction read
it as the latter and dropped the polygon entirely, client-wide, for
every untextured polygon on every object.

Retail's D3DPolyRender::DrawMesh (@0x0059d4a0, named-retail decomp
~line 426048) draws an untextured subset on an ordinary object exactly
like a textured one; the only retail cases that skip an untextured
subset are a building shell (RenderDeviceD3D::DrawBuilding @0x0059f2a0
sets ObjBuildingOrBuildingPart=1) or an EnvCell interior
(RenderDeviceD3D::DrawEnvCell @0x0059f170, arg4=1). The #119
investigation's "retail's skipNoTexture never draws them either"
conclusion was itself wrong as a general rule.

- MeshExtractor.PrepareGfxObjMeshData / GfxObjMesh.Build: emit the
  positive side whenever PosSurface is a valid index, regardless of
  NoPos; the existing UV-index-0 fallback already produces zero
  texcoords for a NoPos polygon with no UVs on the wire.
- RetailUntexturedSurfacePolicy.IsUntextured(SurfaceType): the one
  place that answers "is this surface textured"
  ((type & (Base1Image|Base1ClipMap)) == 0), replacing the old
  `isSolid = NoPos || Base1Solid` (which also mis-classified a NEG-side
  batch by the POS-side's NoPos flag).
- RetailUntexturedSubsetPolicy.Draws(isBuildingShell, isUntextured):
  the shared draw-time gate wired into WbDrawDispatcher.ClassifyBatches,
  .PackedOracle.ClassifyPackedBatches, and
  .DirectionalShadows.AddDirectionalShadowBatches — one predicate so the
  three walks cannot drift (Campaign VM VM6 lesson).
- CellMesh.cs / MeshExtractor.PrepareCellStructMeshData deliberately
  KEEP their NoPos-gated skip for cell-wall geometry — retail's
  DrawEnvCell really does skip untextured subsets there; register row
  AP-234 documents the NoPos-vs-Surface.Type approximation.
- PakFormat.CurrentBakeToolVersion 4->5 (LauncherInstallRecordStore in
  lockstep): a pak baked by an older tool is missing every untextured
  face. No bake was run as part of this commit.

Also fixed: WorldBuilder's own upstream ObjectMeshManager.cs has the
identical NoPos bug (ObjectMeshManager.cs:959,984) — our port had
faithfully carried it over, and our own conformance test
(Build_NoPosFlag_OnlyEmitsNegSide) asserted the bug as correct WB
conformance. Renamed/reworded to Build_NoPosFlag_EmitsBothPosAndNegSide
with a citation for why retail decomp overrides WB here.

Issue119UpNullGfxObjDumpTests re-run against the installed DAT:
#119's own two objects (0x010002B4 9/9 polys, 0x010008A8 1/1 poly) now
gate DRAWS on every polygon instead of extracting to nothing.

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

src/AcDream.App/Rendering/Wb/ObjectMeshManager.cs

@@ -1661,16 +1661,36 @@ namespace AcDream.App.Rendering.Wb
                 var renderData = UploadGfxObjMeshData(meshData);
                 if (renderData == null)
                 {
-                    // 0-vertex mesh: every polygon was gated out at extraction. #119
-                    // (2026-06-11) dat-verified this is LEGITIMATE for all-no-draw
-                    // models (all polys NoPos + Base1Solid surfaces — retail's
-                    // skipNoTexture never draws them either; 0x010002B4/0x010008A8
-                    // are this class, Issue119UpNullGfxObjDumpTests). The empty
-                    // cache is the correct terminal state for those. The line stays
-                    // as a tripwire for the OTHER way to get here (extraction
-                    // dropped textured polys — a real defect; dat-verify with the
-                    // dump test before treating as one).
-                    Console.WriteLine($"[up-null] 0x{meshData.ObjectId:X10} produced a 0-vertex mesh — caching empty render data (legitimate for all-no-draw models; dat-verify via Issue119UpNullGfxObjDumpTests)");
+                    // 0-vertex mesh: every polygon was gated out at extraction.
+                    // #119 (2026-06-11) ORIGINALLY reasoned this is LEGITIMATE
+                    // for every all-NoPos+Base1Solid ("all-no-draw") model,
+                    // claiming retail's skipNoTexture never draws untextured
+                    // subsets at all. #426 (2026-08-23, the Holtburg windmill
+                    // axle 0x010010CE) corrected that: retail's skipNoTexture
+                    // only suppresses untextured subsets on a BUILDING SHELL
+                    // (RenderDeviceD3D::DrawBuilding @0x0059f2a0 sets
+                    // ObjBuildingOrBuildingPart=1) or inside an EnvCell
+                    // interior (DrawEnvCell @0x0059f170, arg4=1) — an
+                    // ORDINARY object's untextured (solid-colour) polygons DO
+                    // draw (D3DPolyRender::DrawMesh(..., arg4=0)). Extraction
+                    // now emits the positive side for every polygon with a
+                    // valid PosSurface regardless of NoPos, so a 0-vertex
+                    // mesh here is legitimate ONLY for a model whose every
+                    // polygon is degenerate (fewer than 3 vertices) or
+                    // references no valid Surface index at all.
+                    // Issue119UpNullGfxObjDumpTests' own dump against the
+                    // installed DAT confirms #119's original two objects
+                    // (0x010002B4, 9 polys; 0x010008A8, 1 poly — both
+                    // all-NoPos+Base1Solid) now gate DRAWS on every polygon
+                    // and are NOT examples of the legitimate 0-vertex case
+                    // any more; they were never actually all-degenerate or
+                    // all-invalid-surface, they were all-solid, which #426
+                    // now extracts. The line stays as a tripwire for the
+                    // OTHER way to get here (extraction dropped textured
+                    // polys — a real defect;
+                    // dat-verify with the dump test before treating a hit as
+                    // legitimate).
+                    Console.WriteLine($"[up-null] 0x{meshData.ObjectId:X10} produced a 0-vertex mesh — caching empty render data (legitimate only for degenerate/no-valid-surface models post-#426; dat-verify via Issue119UpNullGfxObjDumpTests)");
                     renderData = new ObjectRenderData();
                 }
 

src/AcDream.App/Rendering/Wb/WbDrawDispatcher.DirectionalShadows.cs

@@ -1183,6 +1183,15 @@ public sealed partial class WbDrawDispatcher
              batchIndex++)
         {
             ObjectRenderBatch batch = renderData.Batches[batchIndex];
+
+            // #426: a batch retail never draws for this entity casts no
+            // shadow either — same gate as ClassifyBatches/
+            // ClassifyPackedBatches (RetailUntexturedSubsetPolicy), so the
+            // caster and receiver agree by construction (mirrors the
+            // FoliageWindClassification comment below).
+            if (!RetailUntexturedSubsetPolicy.Draws(candidate.IsBuildingShell, batch.Key.IsSolid))
+                continue;
+
             sourceBatches++;
             if (!DirectionalShadowPreparedDraws.TryClassifyMaterial(
                     batch.Translucency,

src/AcDream.App/Rendering/Wb/WbDrawDispatcher.PackedOracle.cs

@@ -631,6 +631,14 @@ public sealed unsafe partial class WbDrawDispatcher
         {
             ObjectRenderBatch batch =
                 renderData.Batches[batchIndex];
+
+            // #426: mirrors the classic ClassifyBatches gate exactly — see
+            // RetailUntexturedSubsetPolicy for the retail citation. ONE
+            // shared predicate so the classic and packed classifiers cannot
+            // drift (Campaign VM VM6).
+            if (!RetailUntexturedSubsetPolicy.Draws(entity.IsBuildingShell, batch.Key.IsSolid))
+                continue;
+
             TranslucencyKind translucency = batch.Translucency;
             if (opacity < 1f && IsOpaque(translucency))
                 translucency = TranslucencyKind.AlphaBlend;

src/AcDream.App/Rendering/Wb/WbDrawDispatcher.cs

@@ -3421,6 +3421,15 @@ public sealed partial class WbDrawDispatcher : IDisposable
         {
             var batch = renderData.Batches[batchIdx];
 
+            // #426: retail's D3DPolyRender::DrawMesh skips an UNTEXTURED
+            // (solid-colour) subset only on a BUILDING SHELL
+            // (RenderDeviceD3D::DrawBuilding sets ObjBuildingOrBuildingPart);
+            // ordinary statics/scenery/creatures/items draw it same as any
+            // textured subset. ONE shared predicate with ClassifyPackedBatches
+            // and AddDirectionalShadowBatches — see RetailUntexturedSubsetPolicy.
+            if (!RetailUntexturedSubsetPolicy.Draws(entity.IsBuildingShell, batch.Key.IsSolid))
+                continue;
+
             TranslucencyKind translucency = batch.Translucency;
 
             // #188: a mid-fade instance whose surface is otherwise Opaque/ClipMap