fix(chargen): Campaign CC CC6b-PRE review fix round — F1-F7 + F11 concession rewrite

F1 (BLOCKING, doc-only) — the idle-by-default rationale rested on an unsound
"uninitialized C++ member defaults to 0" argument (heap operator-new memory
is indeterminate, not zero). Verified and replaced with the real evidence:
gmCGAppearancePage::InitializePage @0x0047FDD0 writes an EXPLICIT
this->m_bZoomedIn = 0; at 0x004802C3, immediately after that same function
points the camera at the zoomed-IN per-heritage eye (0x00480286-0x0048029E).
Fixed in all three places: the register's TS-83 retirement clause,
ChargenPreviewAnimator's class doc, ChargenPreviewZoomController.IsZoomedIn's
doc. Recorded the retail quirk this implies: the character starts framed
close-up while not-zoomed-in, so the first Zoom In click (once mounted)
tweens close-eye->close-eye (visually null) while still freezing the
animation — the port reproduces this faithfully.

F2 — ChargenPreviewZoomController and ChargenPreviewAnimator kept
independent _zoomedIn bools synced only via a nullable animator parameter,
risking desync. Retail's m_bZoomedIn is a single field gating both camera
and animation, so the fix makes the animator the sole state owner:
ChargenPreviewZoomController now takes its ChargenPreviewAnimator as a
required constructor dependency, IsZoomedIn reads straight through to it,
and ZoomIn/ZoomOut no longer take a parameter at all — there is no second
bool left to disagree.

F3 — documented the DoRotation counter-clockwise branch's x87-stack
decompiler artifact (BN renders x87_r7_1 = x87_r6_3 at 0x0047CAEB, which
would store delta-degrees instead of the timestamp for CCW only); the port
already stores "now" in both branches, cited against
feedback_bn_decomp_field_names.md.

F4 — ChargenPreviewAnimator.ApplyIdleFrame now double-buffers two
List<MeshRef> instead of allocating fresh every 30fps tick.

F5 — filed docs/ISSUES.md #402 tracking the RetailAnimationCyclePlayback /
LiveEntityAnimationPresenter duplication as an owned post-CC follow-up,
referenced from the new type's own doc.

F6 — reworded the ChargenPreviewEntityBuilder.TryBuild "byte-identical"
claim to result-identical (TryBuildAnimated now also resolves the idle DID
and loads the idle Animation before the wrapper discards them).

F7 — added the missing clockwise >360 clamp test (readable decomp
polarity, unlike F3's CCW artifact).

ALSO — rewrote the CC6b ledger row's m_alternateSetupID MUST-COVER note per
the reviewer's F11 concession: all five write sites belong to gmBarberUI
(the post-creation barber shop), not gmCGAppearancePage, which has no
option-checkbox-equivalent field at all. Added the enclosing-function
citations and an explicit directive that CC6b-mount must NOT build a
crown/no-flame checkbox on the Appearance page.

Tests: ChargenPreviewRotationControllerTests +1 (10 total),
ChargenPreviewZoomControllerTests +2 and every case rewritten for the
required-animator constructor (9 total). Core.Tests 4786/1 skip (unchanged),
Content.Tests 147/0, App.Tests 5152/6 skips (+3) — zero failures in
isolation, full solution Release build green. Two pre-existing flakes
observed across repeated full-solution runs, neither caused by this round
and neither reproducing standalone: Core.Net.Tests' NakEmissionTests loss
soak, and Content.Tests' DecodedTextureCacheTests concurrency race.

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

src/AcDream.App/Rendering/ChargenPreviewAnimator.cs

@@ -26,6 +26,17 @@ namespace AcDream.App.Rendering;
 /// at frame 0 on every transition INTO the playing state for the same
 /// reason: <c>set_sequence_animation</c>'s <c>arg3=1</c> clears the sequence
 /// before appending, so every <c>StartAnimation</c> call restarts the clip.
+/// The DEFAULT-false claim itself rests on <c>gmCGAppearancePage::InitializePage
+/// @ 0x0047FDD0</c>'s explicit <c>this-&gt;m_bZoomedIn = 0;</c> at
+/// <c>0x004802C3</c> — written immediately after that same function sets the
+/// camera to the zoomed-IN per-heritage eye (<c>0x00480286-0x0048029E</c>),
+/// not from the ctor simply never touching the field (heap <c>operator new</c>
+/// memory is indeterminate, not zero — that argument doesn't hold on its
+/// own). One retail quirk this implies: the character starts framed close-up
+/// AND not-zoomed-in at the same time, so the FIRST Zoom In click (once
+/// mounted) tweens close-eye→close-eye — visually null — while still
+/// freezing the animation; the port reproduces this faithfully rather than
+/// treating it as a bug.
 /// </para>
 ///
 /// <para>
@@ -47,6 +58,15 @@ internal sealed class ChargenPreviewAnimator
     private float _currFrame;
     private bool _zoomedIn;
 
+    // Double-buffered so a 30fps Tick doesn't allocate a fresh List<MeshRef>
+    // every frame: one buffer is whatever Entity.MeshRefs currently points
+    // at (potentially still being read by the renderer's own Render() call
+    // for this frame), the other is safe to Clear()+refill for the NEXT
+    // tick and only gets published once fully populated.
+    private readonly List<MeshRef> _meshRefsBufferA = [];
+    private readonly List<MeshRef> _meshRefsBufferB = [];
+    private bool _nextBufferIsA = true;
+
     public ChargenPreviewAnimator(ChargenPreviewAnimatedBuild build)
     {
         _build = build ?? throw new ArgumentNullException(nameof(build));
@@ -112,7 +132,9 @@ internal sealed class ChargenPreviewAnimator
     {
         DatReaderWriter.DBObjs.Animation animation = _build.IdleAnimation!;
         IReadOnlyList<ChargenPreviewDrawablePart> parts = _build.DrawableParts;
-        var meshRefs = new List<MeshRef>(parts.Count);
+        List<MeshRef> meshRefs = _nextBufferIsA ? _meshRefsBufferA : _meshRefsBufferB;
+        _nextBufferIsA = !_nextBufferIsA;
+        meshRefs.Clear();
         foreach (ChargenPreviewDrawablePart part in parts)
         {
             bool resolved = RetailAnimationCyclePlayback.TryInterpolatePart(