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/OnlineSessionBrowserUI.cs

@@ -11,8 +11,8 @@ using UnityEngine.InputSystem;
 /// uGUI binding for <see cref="OnlineSessionManager"/>. Drives the server-browser canvas - Host / Refresh /
 /// pick a row / Join / Disconnect plus a status line - and mirrors the manager's state through its
 /// <see cref="OnlineSessionManager.Changed"/> / <see cref="OnlineSessionManager.SessionsChanged"/> events.
-/// Replaces the old IMGUI browser. Lives on the browser canvas; the session logic stays on the
-/// NetworkManager's <see cref="OnlineSessionManager"/>.
+/// Lives on the browser canvas; the session logic stays on the NetworkManager's
+/// <see cref="OnlineSessionManager"/>.
 ///
 /// Selection model: Refresh fills the list with clones of <see cref="entryTemplate"/> (each a clickable row
 /// showing name + player count). Clicking a row selects it; Join connects to the selected session. While
@@ -66,7 +66,7 @@ public class OnlineSessionBrowserUI : MonoBehaviour
 
     private bool _open;                   // Esc-toggled visibility while connected
     private bool _connected;              // last-seen connection state (to detect transitions)
-    private string _lastScene;            // last-seen active scene name (to auto-close on a scene change)
+    private Scene _lastScene;             // last-seen active scene (to auto-close on a scene change)
     private string _disconnectText;       // last applied caption (avoids per-frame TMP churn)
 
     private void Awake()
@@ -122,8 +122,9 @@ public class OnlineSessionBrowserUI : MonoBehaviour
 
         // Auto-close the overlay if the scene changed underneath it (a remote ended/started the match, or
         // we walked into Start Match) so it never lingers as a stale pause across a transition.
-        string scene = SceneManager.GetActiveScene().name;
-        if (connected && _open && _lastScene != null && scene != _lastScene)
+        // Compared as Scene structs (handles), not names, so nothing is allocated per frame.
+        Scene scene = SceneManager.GetActiveScene();
+        if (connected && _open && _lastScene.IsValid() && scene != _lastScene)
             SetOpen(false);
         _lastScene = scene;
 
@@ -301,12 +302,13 @@ public class OnlineSessionBrowserUI : MonoBehaviour
         return t ? t.GetComponent<TMP_Text>() : null;
     }
 
+    // NOT TypingGuard-gated (GameplayKeyPressed): Esc must close the panel even while a text field has focus.
     private static bool EscapePressed()
     {
 #if ENABLE_INPUT_SYSTEM
-        return Keyboard.current != null && Keyboard.current.escapeKey.wasPressedThisFrame;
+        return InputUtil.KeyPressedThisFrame(Key.Escape);
 #else
-        return Input.GetKeyDown(KeyCode.Escape);
+        return InputUtil.KeyPressedThisFrame(KeyCode.Escape);
 #endif
     }
 }