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>

.gitattributes

@@ -0,0 +1,49 @@
+# Unity .gitattributes
+# Normalize line endings: text files use LF in the repo, native on checkout.
+* text=auto
+
+# Unity YAML / text-based assets (serialized as text)
+*.cs        text diff=csharp
+*.shader    text
+*.cginc     text
+*.hlsl      text
+*.compute   text
+*.meta      text eol=lf
+*.unity     text eol=lf merge=union
+*.asset     text eol=lf merge=union
+*.prefab    text eol=lf merge=union
+*.mat       text eol=lf merge=union
+*.anim      text eol=lf merge=union
+*.controller text eol=lf merge=union
+*.physicMaterial text eol=lf merge=union
+*.inputactions text eol=lf
+*.json      text
+*.txt       text
+*.md        text
+
+# Binary assets — never apply line-ending or text conversion
+*.fbx       binary
+*.FBX       binary
+*.obj       binary
+*.blend     binary
+*.png       binary
+*.jpg       binary
+*.jpeg      binary
+*.gif       binary
+*.tga       binary
+*.psd       binary
+*.tif       binary
+*.tiff      binary
+*.exr       binary
+*.hdr       binary
+*.wav       binary
+*.mp3       binary
+*.ogg       binary
+*.aif       binary
+*.ttf       binary
+*.otf       binary
+*.unitypackage binary
+*.dll       binary
+*.so        binary
+*.a         binary
+*.dylib     binary