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.Cpu.cs

@@ -34,8 +34,7 @@ public partial class MeshPainter
     /// <summary>CPU pixels are stored directly in material layout; just guarantee a sane alpha for the color maps.</summary>
     private Color32[] SeedCpuPixels(int mi, Color32[][] canonical)
     {
-        var src = (canonical != null && canonical[mi] != null && canonical[mi].Length == textureSize * textureSize)
-            ? canonical[mi] : _seedCanonical[mi];
+        var src = ResolveSeed(mi, canonical);
         var px = (Color32[])src.Clone();
         if (mi != MAP_MSO) // albedo / emission: opaque. The mask map keeps alpha = smoothness.
             for (int i = 0; i < px.Length; i++) px[i].a = 255;