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/ChargenPreviewRotationController.cs

@@ -46,12 +46,54 @@ internal sealed class ChargenPreviewRotationController
     private ChargenRotateDirection _direction = ChargenRotateDirection.Invalid;
     private bool _rotating;
 
+    /// <summary>
+    /// CC6b-MOUNT: retail's true OPERATIVE starting heading — not the ctor's
+    /// value. <c>gmCGAppearancePage::gmCGAppearancePage @0x0047CCC0</c> sets
+    /// <c>m_fCurHeading = 0f</c> at <c>0x0047CDAC</c>, but
+    /// <c>gmCGAppearancePage::InitializePage @0x0047FDD0</c> — which always
+    /// runs immediately afterward, before the page is ever visible — writes
+    /// <c>m_fCurHeading = 180f</c> at <c>0x00480235</c> and pushes it into the
+    /// view via <c>gmCG3DView::SetPlayerHeading(m_p3DView, 180f)</c> at
+    /// <c>0x0048023F</c>. No player-visible frame of chargen's Appearance
+    /// preview is EVER rendered at the ctor's 0° — 180° is the only heading a
+    /// user actually sees. The same override, independently, is what every
+    /// other <c>gmCG3DView</c> owner does for ITS own instance:
+    /// <c>gmCGSummaryPage::InitializePage @0x0047BD54</c> (a separate
+    /// viewport/page, CC5's scope, not this one) and
+    /// <c>gmBarberUI::PostInit</c> (~<c>0x004DE330</c>, pushed at
+    /// <c>0x004E03B5</c>) both call the identical
+    /// <c>SetPlayerHeading(m_p3DView, 180f)</c> for their own pages. Since
+    /// this controller — like retail's <c>m_fCurHeading</c> — is itself the
+    /// PAGE-level heading owner (not the view's), matching the value every
+    /// real page converges on before its first frame is the retail-faithful
+    /// choice; requiring every future mount site to remember a separate
+    /// "seed to 180" call would be a trap (a forgotten seed silently faces
+    /// the character away from the camera).
+    /// </summary>
+    public const float RetailDefaultHeadingDegrees = 180f;
+
     public bool IsRotating => _rotating;
     public ChargenRotateDirection Direction => _direction;
 
-    /// <summary>Retail's <c>m_fCurHeading</c>, degrees, ctor default 0 —
-    /// applied to the preview entity via <c>MoveToMath.SetHeading</c>
-    /// (<c>CPhysicsObj::set_heading</c>'s exact port).</summary>
+    /// <param name="initialHeadingDegrees">Defaults to
+    /// <see cref="RetailDefaultHeadingDegrees"/> (see that constant's doc for
+    /// the full ctor-vs-InitializePage citation) — the value every real
+    /// mount site should get for free. Tests that exercise the pure
+    /// rotation/wrap arithmetic pass <c>0f</c> explicitly for simpler
+    /// relative-delta assertions; that is a test convenience, not a second
+    /// retail-cited default.</param>
+    public ChargenPreviewRotationController(
+        float initialHeadingDegrees = RetailDefaultHeadingDegrees)
+    {
+        HeadingDegrees = initialHeadingDegrees;
+    }
+
+    /// <summary>Retail's <c>m_fCurHeading</c>, degrees — applied to the
+    /// preview entity via <c>MoveToMath.SetHeading</c>
+    /// (<c>CPhysicsObj::set_heading</c>'s exact port). See
+    /// <see cref="RetailDefaultHeadingDegrees"/> for why this controller's
+    /// parameterless-constructor default is 180, not the ctor's raw 0.
+    /// </summary>
     public float HeadingDegrees { get; private set; }
 
     /// <summary>