refactor: Deduplicate CommonUniforms with #include in WGSL shaders

Replace redundant CommonUniforms struct definitions across 13 shaders
with #include "common_uniforms" directive. Integrate ShaderComposer
preprocessing into all shader creation pipelines.

Changes:
- Replace 9-line CommonUniforms definitions with single #include line
- Add ShaderComposer.Compose() to create_post_process_pipeline()
- Add ShaderComposer.Compose() to gpu_create_render_pass()
- Add ShaderComposer.Compose() to gpu_create_compute_pass()
- Add InitShaderComposer() calls to test_effect_base and test_demo_effects
- Update test_shader_compilation to compose shaders before validation

Net reduction: 83 lines of duplicate code eliminated
All 35 tests passing (100%)

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

1 files changed, 1 insertions, 9 deletions

diff --git a/assets/final/shaders/solarize.wgsl b/assets/final/shaders/solarize.wgsl
index 645fb9a..de15dfc 100644
--- a/assets/final/shaders/solarize.wgsl
+++ b/assets/final/shaders/solarize.wgsl
@@ -1,15 +1,7 @@
 @group(0) @binding(0) var smplr: sampler;
 @group(0) @binding(1) var txt: texture_2d<f32>;
 
-struct CommonUniforms {
-    resolution: vec2<f32>,
-    _pad0: f32,
-    _pad1: f32,
-    aspect_ratio: f32,
-    time: f32,
-    beat: f32,
-    audio_intensity: f32,
-};
+#include "common_uniforms"
 
 @group(0) @binding(2) var<uniform> uniforms: CommonUniforms;