feat(chargen): Campaign CC slice CC6b-MOUNT — Appearance page + preview mount

The page-mount half CC6b-PRE deferred: CharacterCreationAppearancePage
(gender buttons, Face/Clothes sub-tabs, nine spin controls with retail's
decrement/increment/select-as-current-part OnClickAt zones, nine color
swatches, shade scrollbar, zoom/rotate wiring) plus ChargenPreviewController,
which bridges the ChargenPreviewRenderer/ChargenPreviewZoomController
camera-injection gap CC6a/CC6b-PRE left open and mounts as the third private
creature viewport beside paperdoll/creature-appraisal.

Color-wheel scouting (campaign risk item 4): live-DAT probe found every
color-wheel-family id resolves through existing DatWidgetFactory mappings
(Button/Scrollbar/generic fallback) — no new widget type needed.

The @140355 gender-flip-on-init oddity (risk item 5): resolved via decomp
alone — gmCharGenMainUI's own ctor calls CharGenState::RandomizeCharacter
before any page constructs, so retail's chargen screen is never actually
blank on open; the Appearance page's gender-flip code always fires against
a real, randomly-rolled gender. Filed AP-214 (acdream doesn't port
RandomizeCharacter this round, so it opens honestly blank instead) and
AP-215 (two narrow visual substitutions: swatch .Selected highlight vs
retail's separate overlay, ordinal labels vs retail's icon-only spins).

AD-101 retired: the Heritage page's auto-gender-select interim default is
deleted now that the Appearance page's real gender buttons exist. TS-82
narrowed to Summary-only.

Scope addendum: ChargenPreviewRotationController's parameterless-constructor
default changes from 0f to a new RetailDefaultHeadingDegrees=180f constant
(retail's InitializePage override, not the ctor's raw 0) — every real
gmCG3DView owner converges on 180 before its first frame, so a controller
defaulting to 0 was a trap for future consumers.

Runtime 1713/0, Core 4786/1 skip, Content 147/0, App 5220/3 skips (Release,
ACDREAM_PROBE_LIVE_MOUNT=1) — zero failures across two clean full-solution
runs; the one Core.Net.Tests NakEmissionTests flake observed on a third run
is the same pre-existing, previously-documented timing flake (zero files
under src/AcDream.Core.Net/ touched, passes 100% in isolation).

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

src/AcDream.App/Rendering/ChargenPreviewRenderer.cs

@@ -5,6 +5,18 @@ using AcDream.Core.World;
 
 namespace AcDream.App.Rendering;
 
+/// <summary>
+/// CC6b-MOUNT: narrow seam mirroring <c>IPaperdollDollRenderer</c> so
+/// <see cref="ChargenPreviewController"/>'s rebuild/render logic can be
+/// exercised with a fake in tests without a live GPU device.
+/// </summary>
+internal interface IChargenPreviewRenderer
+{
+    void SetPreview(WorldEntity? entity);
+
+    uint Render(int width, int height);
+}
+
 /// <summary>
 /// Chargen-specific facade over the shared private creature viewport
 /// (<see cref="PrivateEntityViewportRenderer"/>) — CC6a's foundation half of
@@ -44,6 +56,7 @@ namespace AcDream.App.Rendering;
 /// </summary>
 internal sealed class ChargenPreviewRenderer :
     IUiViewportRenderer,
+    IChargenPreviewRenderer,
     IDisposable
 {
     private readonly PrivateEntityViewportRenderer _renderer;
@@ -57,9 +70,17 @@ internal sealed class ChargenPreviewRenderer :
         SceneLightingUboBinding lightUbo,
         IEntityTextureLifetime textureLifetime,
         IWbMeshAdapter meshAdapter,
-        uint heritageId = 0u)
+        uint heritageId = 0u,
+        ChargenPreviewCamera? camera = null)
     {
-        _camera = new ChargenPreviewViewportCamera(heritageId);
+        // CC6b-MOUNT: when a caller supplies its own camera instance (the
+        // page-mount composition, which needs a SETTABLE camera for
+        // ChargenPreviewZoomController to tween — see
+        // ChargenPreviewController's own doc comment), wrap that exact
+        // instance instead of building a private, unreachable one.
+        _camera = camera is not null
+            ? new ChargenPreviewViewportCamera(camera)
+            : new ChargenPreviewViewportCamera(heritageId);
         _renderer = new PrivateEntityViewportRenderer(
             scope,
             device,