Refactor: factorize common WGPU patterns into helper functions

Add texture creation helpers (gpu_create_texture_2d, gpu_create_storage_texture_2d,
gpu_create_mip_view) and extend BindGroupLayoutBuilder with uint_texture and
storage_texture methods.

Refactored files:
- cnn_v2_effect.cc: Use texture helpers (~70% code reduction in create_textures)
- rotating_cube_effect.cc: Use BindGroupLayoutBuilder and texture helpers
- circle_mask_effect.cc: Use BindGroupBuilder

Benefits:
- Improved code readability
- Reduced boilerplate for texture/bind group creation
- Consistent patterns across effects

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

1 files changed, 22 insertions, 0 deletions

diff --git a/src/gpu/bind_group_builder.h b/src/gpu/bind_group_builder.h
index d63f6e2..abce9dc 100644
--- a/src/gpu/bind_group_builder.h
+++ b/src/gpu/bind_group_builder.h
@@ -55,6 +55,28 @@ public:
     return *this;
   }
 
+  BindGroupLayoutBuilder& uint_texture(uint32_t binding, WGPUShaderStageFlags vis) {
+    WGPUBindGroupLayoutEntry e{};
+    e.binding = binding;
+    e.visibility = vis;
+    e.texture.sampleType = WGPUTextureSampleType_Uint;
+    e.texture.viewDimension = WGPUTextureViewDimension_2D;
+    entries_.push_back(e);
+    return *this;
+  }
+
+  BindGroupLayoutBuilder& storage_texture(uint32_t binding, WGPUShaderStageFlags vis,
+                                          WGPUTextureFormat format) {
+    WGPUBindGroupLayoutEntry e{};
+    e.binding = binding;
+    e.visibility = vis;
+    e.storageTexture.access = WGPUStorageTextureAccess_WriteOnly;
+    e.storageTexture.format = format;
+    e.storageTexture.viewDimension = WGPUTextureViewDimension_2D;
+    entries_.push_back(e);
+    return *this;
+  }
+
   BindGroupLayoutBuilder& sampler(uint32_t binding, WGPUShaderStageFlags vis) {
     WGPUBindGroupLayoutEntry e{};
     e.binding = binding;