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/MouseSensitivity.cs

@@ -1,4 +1,3 @@
-using System;
 using UnityEngine;
 
 /// Global mouse look-around sensitivity multiplier, shared by every camera
@@ -15,9 +14,6 @@ public static class MouseSensitivity
     static bool _loaded;
     static float _multiplier = Default;
 
-    /// Fires whenever the multiplier changes (UI may run before the avatar spawns).
-    public static event Action<float> Changed;
-
     public static float Multiplier
     {
         get
@@ -40,7 +36,6 @@ public static class MouseSensitivity
             // only a clean quit. Settings changes are rare user actions, so the
             // extra write is negligible.
             PlayerPrefs.Save();
-            Changed?.Invoke(v);
         }
     }
 }