refactor: use CommonUniforms from common_uniforms.wgsl in test_demo

Instead of duplicating the uniform structure definition, PeakMeterEffect
now uses ShaderComposer to include the common_uniforms snippet, ensuring
the struct definition always matches the canonical version.

Changes:
- Added shader_composer.h include
- Use ShaderComposer::Get().Compose() to prepend common_uniforms
- Changed 'Uniforms' → 'CommonUniforms' in shader
- Removed duplicate struct definition

This ensures consistency across all shaders and eliminates potential
drift between duplicate definitions.

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

1 files changed, 10 insertions, 14 deletions

diff --git a/src/test_demo.cc b/src/test_demo.cc
index 595ca6a..b564b9b 100644
--- a/src/test_demo.cc
+++ b/src/test_demo.cc
@@ -21,33 +21,25 @@ extern void LoadTimeline(MainSequence& main_seq, const GpuContext& ctx);
 
 // Inline peak meter effect for debugging audio-visual sync
 #include "gpu/effects/post_process_helper.h"
+#include "gpu/effects/shader_composer.h"
+
 class PeakMeterEffect : public PostProcessEffect {
  public:
   PeakMeterEffect(const GpuContext& ctx) : PostProcessEffect(ctx) {
-    // Use standard post-process binding macros
-    const char* shader_code = R"(
+    // Use ShaderComposer to include CommonUniforms from common_uniforms.wgsl
+    const char* shader_main = R"(
       struct VertexOutput {
         @builtin(position) position: vec4<f32>,
         @location(0) uv: vec2<f32>,
       };
 
-      struct Uniforms {
-        resolution: vec2<f32>,
-        aspect_ratio: f32,
-        time: f32,
-        beat_time: f32,
-        beat_phase: f32,
-        audio_intensity: f32,
-        _pad: f32,
-      };
-
       struct EffectParams {
         unused: f32,
       };
 
       @group(0) @binding(0) var inputSampler: sampler;
       @group(0) @binding(1) var inputTexture: texture_2d<f32>;
-      @group(0) @binding(2) var<uniform> uniforms: Uniforms;
+      @group(0) @binding(2) var<uniform> uniforms: CommonUniforms;
       @group(0) @binding(3) var<uniform> params: EffectParams;
 
       @vertex
@@ -86,8 +78,12 @@ class PeakMeterEffect : public PostProcessEffect {
       }
     )";
 
+    // Compose shader with common_uniforms to get CommonUniforms definition
+    std::string shader_code = ShaderComposer::Get().Compose(
+        {"common_uniforms"}, shader_main);
+
     pipeline_ =
-        create_post_process_pipeline(ctx_.device, ctx_.format, shader_code);
+        create_post_process_pipeline(ctx_.device, ctx_.format, shader_code.c_str());
   }
 
   void update_bind_group(WGPUTextureView input_view) {