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.Spray.cs

@@ -143,13 +143,7 @@ public partial class MeshPainter
     {
         if (_sprayTex) return;
 
-        _sprayTex = new Texture2D(SprayRes, SprayRes, TextureFormat.RGBA32, false, true) // linear: raw mask values
-        {
-            name = "MeshPainter_SprayMask",
-            wrapMode = TextureWrapMode.Clamp,
-            filterMode = FilterMode.Bilinear,
-            hideFlags = HideFlags.HideAndDontSave
-        };
+        _sprayTex = NewMaskTexture(SprayRes, "MeshPainter_SprayMask");
         _sprayPixels = new Color32[SprayRes * SprayRes];
         _sprayOpacity = new float[SprayRes * SprayRes];
     }