Refactor: extract shared helpers across scripts, trim remaining doc redundancy

Deduplication pass (44 extractions):
- New SmoothedLook: shared smoothed yaw/pitch look tick + view seeding
  (FirstPersonController, FreeCamController)
- New CharacterTeleport: disable-CC-around-teleport idiom (rescue,
  owner position apply, free-cam sync)
- New GeometryUtil: RescaleToUnitScale + TransformBounds (concealment
  meter/volume, skinned collider baker)
- Paint family: canonical map read/write shared between Net and
  Persistence, snapshot decode, backend stroke dispatch, RebuildBackend,
  ResolveSeed, chunked RPC send/gate/copy, CamoKnobs/HeightKnobs
  aggregates, SanitizeFileKey, NewMaskTexture, AdoptAlbedo, FindSlider
- Player/modes: GameMode SetPlayerControl/SetPainting/SetOrbitInputEnabled,
  InputUtil.GameplayKeyPressed, NearestClimbHit, ComputeXRay delegates to
  ComputeResolutionFreeze, FingerIK TryInPlaneAngle
- Match/misc: UnhookSessionCallbacks, SendEmptyNamedMessage, SwapScenes,
  RunSessionOpAsync, CovarianceEigen, CollectClusterPoints, MatchHud
  GUIStyle cache, HsvColorPicker rehook, VoxelCenter

Documentation pass: remove 6 triplicated doc blocks and 2 restating
inline comments left after the previous reduction.

Behavior-neutral; hot-path rasterizer loops intentionally untouched.

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

Assets/Scripts/MeshPainter.Undo.cs

@@ -209,10 +209,17 @@ public partial class MeshPainter
 
     private void RestoreCurrentState()
     {
-        ReseedCanonical(_undoStates[_undoIndex]);
+        RestoreEntry(_undoIndex);
+        OnHistoryRestore?.Invoke(_undoIds[_undoIndex]); // owner -> peers reproduce the move by id
+    }
+
+    /// <summary>Shows history entry <paramref name="idx"/>: re-seeds the backend and clears any in-progress stroke.</summary>
+    private void RestoreEntry(int idx)
+    {
+        _undoIndex = idx;
+        ReseedCanonical(_undoStates[idx]);
         _strokeActive = false;
         _strokeDirtyMaps = 0;
-        OnHistoryRestore?.Invoke(_undoIds[_undoIndex]); // owner -> peers reproduce the move by id
     }
 
     /// <summary>
@@ -225,10 +232,7 @@ public partial class MeshPainter
         int idx = _undoIds.IndexOf(id);
         if (idx < 0) return false;
 
-        _undoIndex = idx;
-        ReseedCanonical(_undoStates[idx]);
-        _strokeActive = false;
-        _strokeDirtyMaps = 0;
+        RestoreEntry(idx);
         return true;
     }