Refactor scripts: dedup remainder, remove dead code, perf hardening

Iteration 4 over Assets/Scripts (no component/file splits, no Unity assets touched):

Dedup:
- Route inline cursor-release, material guards, Ctrl-held and undo/redo
  input through existing InputUtil / SetMatFloat helpers
- Add ungated InputUtil.KeyPressedThisFrame; GameplayKeyPressed builds on it
- Unify FindDeep/FindDeepChild into GeometryUtil.FindDeep

Dead code / stale docs:
- Remove unused code-gen bake path (HsvColorPicker.Build, PaintHud factory)
- Drop unreferenced symbols (SubPhaseChanged event, LocalPhaseDuration,
  IsLocalSceneMain, MouseSensitivity.Changed, IsPaused, InSession,
  NetworkControlled, PreviousPose, JointCount, voxel-count accessors)
- Fix incorrect PlayerRole / PaintHud / Pick / PlayerPose docs

Perf / robustness (behaviour-neutral):
- ConcealmentMeter.Evaluate: reuse vertex/topology buffers, two-pointer
  crossing count
- BuildMeshCaches: alloc-free vertex copy, cached topology/UVs
- Guard all PlayerPaintSync LogSync sites behind logSync
- Cache LocalViewerIsHunter / controller / CanShoot / TypingGuard lookups;
  dedup LocalIsHunter with MatchHud
- Change-guard RefreshEmissionColor and HeroCutout.Disarm
- Cache scene/countdown string comparisons per frame
- Grow NonAlloc buffers and log-once on saturation

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Assets/Scripts/MeshPainter.Undo.cs

@@ -242,24 +242,19 @@ public partial class MeshPainter
         undo = false;
         redo = false;
         if (TypingGuard.IsTyping) return; // let Ctrl+Z/Y edit text instead of the painting
+        if (!InputUtil.CtrlHeld()) return;
 #if ENABLE_INPUT_SYSTEM
         var kb = Keyboard.current;
         if (kb != null)
         {
-            if (kb.leftCtrlKey.isPressed || kb.rightCtrlKey.isPressed)
-            {
-                undo = kb.zKey.wasPressedThisFrame;
-                redo = kb.yKey.wasPressedThisFrame;
-            }
+            undo = kb.zKey.wasPressedThisFrame;
+            redo = kb.yKey.wasPressedThisFrame;
             return;
         }
 #endif
 #if ENABLE_LEGACY_INPUT_MANAGER
-        if (Input.GetKey(KeyCode.LeftControl) || Input.GetKey(KeyCode.RightControl))
-        {
-            undo = Input.GetKeyDown(KeyCode.Z);
-            redo = Input.GetKeyDown(KeyCode.Y);
-        }
+        undo = Input.GetKeyDown(KeyCode.Z);
+        redo = Input.GetKeyDown(KeyCode.Y);
 #endif
     }
 }