refactor(wgsl): modularize common shader functions

Extracted common WGSL functions into separate files in `common/shaders/` to improve reusability and maintainability.

- Created `common/shaders/render/fullscreen_vs.wgsl` for a reusable fullscreen vertex shader.
- Created `common/shaders/math/color.wgsl` for color conversion and tone mapping functions.
- Created `common/shaders/math/utils.wgsl` for general math utilities.
- Created `common/shaders/render/raymarching.wgsl` for SDF raymarching logic.
- Updated multiple shaders to use these new common snippets via `#include`.
- Fixed the shader asset validation test to correctly handle shaders that include the common vertex shader.

This refactoring makes the shader code more modular and easier to manage.

2 files changed, 8 insertions, 1 deletions

diff --git a/src/gpu/post_process_helper.cc b/src/gpu/post_process_helper.cc
index 4ffa9c1..c5bef27 100644
--- a/src/gpu/post_process_helper.cc
+++ b/src/gpu/post_process_helper.cc
@@ -21,8 +21,10 @@ WGPURenderPipeline create_post_process_pipeline(WGPUDevice device,
     .uniform(PP_BINDING_EFFECT_PARAMS, WGPUShaderStage_Fragment)
     .build(device);
 
+  const std::string composed_shader = ShaderComposer::Get().Compose({}, shader_code);
+
   WGPURenderPipeline pipeline = RenderPipelineBuilder(device)
-    .shader(shader_code)
+    .shader(composed_shader.c_str())
     .bind_group_layout(bgl)
     .format(format)
     .build();
diff --git a/src/gpu/shaders.cc b/src/gpu/shaders.cc
index 903b96e..1b50e8e 100644
--- a/src/gpu/shaders.cc
+++ b/src/gpu/shaders.cc
@@ -52,6 +52,11 @@ void InitShaderComposer() {
   register_if_exists("ray_box", AssetId::ASSET_SHADER_RAY_BOX);
   register_if_exists("ray_triangle", AssetId::ASSET_SHADER_RAY_TRIANGLE);
 
+  register_if_exists("render/fullscreen_vs", AssetId::ASSET_SHADER_RENDER_FULLSCREEN_VS);
+  register_if_exists("math/color", AssetId::ASSET_SHADER_MATH_COLOR);
+  register_if_exists("math/utils", AssetId::ASSET_SHADER_MATH_UTILS);
+  register_if_exists("render/raymarching", AssetId::ASSET_SHADER_RENDER_RAYMARCHING);
+
   register_if_exists("cnn_activation", AssetId::ASSET_SHADER_CNN_ACTIVATION);
   register_if_exists("cnn_conv1x1", AssetId::ASSET_SHADER_CNN_CONV1X1);
   register_if_exists("cnn_conv3x3", AssetId::ASSET_SHADER_CNN_CONV3X3);