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/GameModeManager.cs

@@ -62,9 +62,6 @@ public class GameModeManager : MonoBehaviour
     private bool _paused;
     private int _resumeIndex = -1;
 
-    /// <summary>True while local gameplay is suspended for a modal overlay (see <see cref="SetPaused"/>).</summary>
-    public bool IsPaused => _paused;
-
     /// <summary>The currently active mode (null before startup).</summary>
     public GameMode ActiveMode =>
         (_activeIndex >= 0 && _activeIndex < _modes.Count) ? _modes[_activeIndex] : null;
@@ -246,8 +243,7 @@ public class GameModeManager : MonoBehaviour
             cameraInput.LookMode = ThirdPersonOrbitInput.OrbitLookMode.Disabled;
 
         // Belt-and-braces explicit release (covers the orbit input being absent/disabled).
-        Cursor.lockState = CursorLockMode.None;
-        Cursor.visible = true;
+        InputUtil.SetCursorLocked(false);
     }
 
     /// <summary>
@@ -279,8 +275,7 @@ public class GameModeManager : MonoBehaviour
                 cameraInput.enabled = true;
                 cameraInput.LookMode = ThirdPersonOrbitInput.OrbitLookMode.Disabled;
             }
-            Cursor.lockState = CursorLockMode.None;
-            Cursor.visible = true;
+            InputUtil.SetCursorLocked(false);
 
             ModeChanged?.Invoke(null);   // hide mode-following UI (the paint HUD) beneath the overlay
         }