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.Setup.cs

@@ -176,8 +176,6 @@ public partial class MeshPainter
     /// <summary>Builds the albedo base-color texels from the existing material texture or baseColor.</summary>
     private Color32[] BuildBaseColors()
     {
-        var px = new Color32[textureSize * textureSize];
-
         Texture sourceTex = null;
         var shared = _renderer.sharedMaterial;
         if (shared)
@@ -197,9 +195,7 @@ public partial class MeshPainter
             catch { /* not readable -> fall back to baseColor */ }
         }
 
-        Color32 c = baseColor;
-        for (int i = 0; i < px.Length; i++) px[i] = c;
-        return px;
+        return FillCanonical(baseColor);
     }
 
     /// <summary>Enables the URP keywords for the painted PBR maps and seeds the material scalars.</summary>