feat(shaders): Add Möller-Trumbore ray-triangle intersection

Implements ray-triangle intersection algorithm for future mesh raytracing support.

Changes:
- Add ray_triangle.wgsl with TriangleHit struct and intersection function
- Register shader snippet in asset system (SHADER_RAY_TRIANGLE)
- Add shader composer registration for #include "ray_triangle" support

Returns:
- hit.uv: Barycentric coordinates (for texture mapping)
- hit.z: Parametric distance along ray
- hit.N: Triangle face normal
- hit.hit: Boolean indicating intersection

Task: Progress on SDF for mesh (related to Task #18)
Algorithm: Fast, Minimum Storage Ray-Triangle Intersection (Möller-Trumbore)
Size: ~30 lines WGSL, negligible binary impact

1 files changed, 1 insertions, 0 deletions

diff --git a/src/gpu/effects/shaders.cc b/src/gpu/effects/shaders.cc
index dcbb0fd..51e6e41 100644
--- a/src/gpu/effects/shaders.cc
+++ b/src/gpu/effects/shaders.cc
@@ -48,6 +48,7 @@ void InitShaderComposer() {
   register_if_exists("lighting", AssetId::ASSET_SHADER_LIGHTING);
 
   register_if_exists("ray_box", AssetId::ASSET_SHADER_RAY_BOX);
+  register_if_exists("ray_triangle", AssetId::ASSET_SHADER_RAY_TRIANGLE);
 }
 
 // Helper to get asset string or empty string