feat(gpu): Add VignetteEffect and related files

- Implemented VignetteEffect, including its shader, parameters, and sequence integration.
- Added VignetteEffect to demo_effects.h, shaders.cc/h, and asset definitions.
- Updated seq_compiler to handle VignetteEffect parameters.
- Added VignetteEffect to test suite and updated expected counts.
- Ensured all changes build and tests pass.
- Added vignette_effect.cc implementation file.
- Updated CMakeLists.txt to include the new effect file.
- Updated assets/demo.seq to include the VignetteEffect.
- Updated assets/final/demo_assets.txt with the new shader asset.

1 files changed, 33 insertions, 0 deletions

diff --git a/src/gpu/demo_effects.h b/src/gpu/demo_effects.h
index 6c8729d..ad95cfe 100644
--- a/src/gpu/demo_effects.h
+++ b/src/gpu/demo_effects.h
@@ -127,6 +127,39 @@ class DistortEffect : public PostProcessEffect {
   void update_bind_group(WGPUTextureView input_view) override;
 };
 
+// Parameters for VignetteEffect
+struct VignetteParams {
+  float radius = 0.5f;   // Radius of the clear center
+  float softness = 0.5f; // Softness of the vignette edge
+};
+
+// Uniform data for VignetteEffect
+struct VignetteUniforms {
+  float time;         // offset 0
+  float beat;         // offset 4
+  float intensity;    // offset 8
+  float aspect_ratio; // offset 12
+  float width;        // offset 16
+  float height;       // offset 20
+  float radius;       // offset 24
+  float softness;     // offset 28
+};
+static_assert(sizeof(VignetteUniforms) == 32,
+              "VignetteUniforms must be 32 bytes for WGSL alignment");
+
+class VignetteEffect : public PostProcessEffect {
+ public:
+  VignetteEffect(const GpuContext& ctx);
+  VignetteEffect(const GpuContext& ctx, const VignetteParams& params);
+  void render(WGPURenderPassEncoder pass, float time, float beat,
+              float intensity, float aspect_ratio) override;
+  void update_bind_group(WGPUTextureView input_view) override;
+
+ private:
+  VignetteParams params_;
+  UniformBuffer<VignetteUniforms> uniforms_;
+};
+
 // Parameters for ChromaAberrationEffect (set at construction time)
 struct ChromaAberrationParams {
   float offset_scale = 0.02f; // Default: 2% screen offset