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.Net.cs

@@ -139,18 +139,9 @@ public partial class MeshPainter
         if (spray) BuildSprayStampMaskSeeded(s.SpraySeed);
         else { ResolveActiveMask(); UseResolvedStampMask(); }
 
-        if (_gpuActive)
-        {
-            BeginGpuStroke();
-            DrawBrushGpu(s.P, s.R, s.U, s.V, s.N);
-            EndGpuStroke();
-        }
-        else
-        {
-            ResetCpuDirty();
-            PaintStamp3D(s.P, s.R, s.U, s.V, s.N);
-            EndCpuStroke();
-        }
+        BeginBackendStroke();
+        DrawBackendStamp(s.P, s.R, s.U, s.V, s.N);
+        EndBackendStroke();
 
         // Accumulate this peer's stroke dirty mask so a network checkpoint marker can commit the same
         // history entry as the owner (same stamps -> same touched maps -> COW-aligned with the owner).
@@ -189,21 +180,7 @@ public partial class MeshPainter
                 w.Write(textureSize);
                 w.Write(MAP_COUNT);
 
-                var bytes = new byte[n * 4];
-                for (int mi = 0; mi < MAP_COUNT; mi++)
-                {
-                    Color32[] px = ReadCanonical(mi);
-                    int count = Mathf.Min(n, px.Length);
-                    for (int i = 0; i < count; i++)
-                    {
-                        int o = i * 4;
-                        bytes[o] = px[i].r;
-                        bytes[o + 1] = px[i].g;
-                        bytes[o + 2] = px[i].b;
-                        bytes[o + 3] = px[i].a;
-                    }
-                    w.Write(bytes, 0, count * 4);
-                }
+                WriteCanonicalMaps(w);
             }
             compressed = Deflate(raw.ToArray());
         }
@@ -217,19 +194,8 @@ public partial class MeshPainter
     /// </summary>
     public void ApplyPaintSnapshot(byte[] compressed, int baselineId)
     {
-        if (!_setupValid || compressed == null || compressed.Length == 0) return;
+        if (!TryDecodeSnapshot(compressed, "Paint", out Color32[][] canonical)) return;
 
-        Color32[][] canonical;
-        try { canonical = DecodeSnapshot(compressed); }
-        catch (System.Exception e)
-        {
-            Debug.LogWarning($"[MeshPainter] Paint snapshot decode failed: {e.Message}", this);
-            return;
-        }
-        if (canonical == null) return;
-
-        // Re-seed exactly like SwitchBackend, but with externally supplied maps, so the island/dilation
-        // seeding path runs and the edge padding is rebuilt correctly for the loaded content.
         ReseedCanonical(canonical);
         SetHistoryBaseline(canonical, baselineId);
     }
@@ -242,22 +208,28 @@ public partial class MeshPainter
     /// </summary>
     public bool LoadPaintFromSnapshot(byte[] compressed)
     {
-        if (!_setupValid || compressed == null || compressed.Length == 0) return false;
-
-        Color32[][] canonical;
-        try { canonical = DecodeSnapshot(compressed); }
-        catch (System.Exception e)
-        {
-            Debug.LogWarning($"[MeshPainter] Carry snapshot decode failed: {e.Message}", this);
-            return false;
-        }
-        if (canonical == null) return false;
+        if (!TryDecodeSnapshot(compressed, "Carry", out Color32[][] canonical)) return false;
 
         ReseedCanonical(canonical);
         ResetHistoryToCurrent(canonical);
         return true;
     }
 
+    /// <summary>Guard + decode for an incoming snapshot blob; false = not ready / empty / undecodable.</summary>
+    private bool TryDecodeSnapshot(byte[] compressed, string context, out Color32[][] canonical)
+    {
+        canonical = null;
+        if (!_setupValid || compressed == null || compressed.Length == 0) return false;
+
+        try { canonical = DecodeSnapshot(compressed); }
+        catch (System.Exception e)
+        {
+            Debug.LogWarning($"[MeshPainter] {context} snapshot decode failed: {e.Message}", this);
+            return false;
+        }
+        return canonical != null;
+    }
+
     private Color32[][] DecodeSnapshot(byte[] compressed)
     {
         byte[] raw = Inflate(compressed);
@@ -272,22 +244,7 @@ public partial class MeshPainter
             // Resolution / version mismatch: ignore rather than smear; the painter keeps its state.
             if (ver != SnapshotVersion || size != textureSize) return null;
 
-            int n = textureSize * textureSize;
-            var result = new Color32[MAP_COUNT][];
-            int load = Mathf.Min(maps, MAP_COUNT);
-            for (int mi = 0; mi < load; mi++)
-            {
-                byte[] b = r.ReadBytes(n * 4);
-                if (b.Length != n * 4) break; // truncated -> remaining maps stay at the material seed
-                var px = new Color32[n];
-                for (int i = 0; i < n; i++)
-                {
-                    int o = i * 4;
-                    px[i] = new Color32(b[o], b[o + 1], b[o + 2], b[o + 3]);
-                }
-                result[mi] = px;
-            }
-            return result;
+            return ReadCanonicalMaps(r, maps);
         }
     }