Initial commit: Unity mesh painter project

Unity 6000.3 (URP) project with live mesh painting in play mode.

- MeshPainter.cs: paint a SkinnedMesh with the mouse, seamless across
  UV islands via 3D-space painting, GPU and CPU backends (switchable),
  edge-padding/dilation against bilinear seam bleed
- FrameRateLimiter.cs: simple frame rate limiting component
- MeshPaintBrush / MeshPaintDilate shaders for the GPU paint path
- Unity-specific .gitignore and .gitattributes

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

ProjectSettings/DynamicsManager.asset

@@ -0,0 +1,36 @@
+%YAML 1.1
+%TAG !u! tag:unity3d.com,2011:
+--- !u!55 &1
+PhysicsManager:
+  m_ObjectHideFlags: 0
+  serializedVersion: 13
+  m_Gravity: {x: 0, y: -9.81, z: 0}
+  m_DefaultMaterial: {fileID: 0}
+  m_BounceThreshold: 2
+  m_SleepThreshold: 0.005
+  m_DefaultContactOffset: 0.01
+  m_DefaultSolverIterations: 6
+  m_DefaultSolverVelocityIterations: 1
+  m_QueriesHitBackfaces: 0
+  m_QueriesHitTriggers: 1
+  m_EnableAdaptiveForce: 0
+  m_ClothInterCollisionDistance: 0.1
+  m_ClothInterCollisionStiffness: 0.2
+  m_ContactsGeneration: 1
+  m_LayerCollisionMatrix: ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff
+  m_AutoSimulation: 1
+  m_AutoSyncTransforms: 0
+  m_ReuseCollisionCallbacks: 1
+  m_ClothInterCollisionSettingsToggle: 0
+  m_ClothGravity: {x: 0, y: -9.81, z: 0}
+  m_ContactPairsMode: 0
+  m_BroadphaseType: 0
+  m_WorldBounds:
+    m_Center: {x: 0, y: 0, z: 0}
+    m_Extent: {x: 250, y: 250, z: 250}
+  m_WorldSubdivisions: 8
+  m_FrictionType: 0
+  m_EnableEnhancedDeterminism: 0
+  m_EnableUnifiedHeightmaps: 1
+  m_SolverType: 0
+  m_DefaultMaxAngularSpeed: 50