refactor: Simplify effect render API and fix uniform initialization

Root cause: Uniform buffers created but not initialized before bind group
creation, causing undefined UV coordinates in circle_mask_compute.wgsl.

Changes:
- Add get_common_uniforms() helper to Effect base class
- Refactor render()/compute() signatures: 5 params → CommonPostProcessUniforms&
- Fix uninitialized uniforms in CircleMaskEffect and CNNEffect
- Update all 19 effect implementations and headers
- Fix WGSL syntax error in FlashEffect (u.audio_intensity → audio_intensity)
- Update test files (test_sequence.cc)

Benefits:
- Cleaner API: construct uniforms once per frame, reuse across effects
- More maintainable: CommonPostProcessUniforms changes need no call site updates
- Fixes UV coordinate bug in circle_mask_compute.wgsl

All 36 tests passing (100%)

handoff(Claude): Effect API refactor complete

1 files changed, 7 insertions, 14 deletions

diff --git a/src/gpu/effects/fade_effect.cc b/src/gpu/effects/fade_effect.cc
index 39b54e0..93684d8 100644
--- a/src/gpu/effects/fade_effect.cc
+++ b/src/gpu/effects/fade_effect.cc
@@ -72,26 +72,19 @@ void FadeEffect::update_bind_group(WGPUTextureView input_view) {
                        uniforms_.get(), params_buffer_);
 }
 
-void FadeEffect::render(WGPURenderPassEncoder pass, float time, float beat,
-                        float intensity, float aspect_ratio) {
-  const CommonPostProcessUniforms u = {
-      .resolution = {(float)width_, (float)height_},
-      .aspect_ratio = aspect_ratio,
-      .time = time,
-      .beat = beat,
-      .audio_intensity = intensity,
-  };
-  uniforms_.update(ctx_.queue, u);
+void FadeEffect::render(WGPURenderPassEncoder pass,
+                        const CommonPostProcessUniforms& uniforms) {
+  uniforms_.update(ctx_.queue, uniforms);
 
   // Example fade pattern: fade in at start, fade out at end
   // Customize this based on your needs
   float fade_amount = 1.0f;
-  if (time < 2.0f) {
+  if (uniforms.time < 2.0f) {
     // Fade in from black over first 2 seconds
-    fade_amount = time / 2.0f;
-  } else if (time > 36.0f) {
+    fade_amount = uniforms.time / 2.0f;
+  } else if (uniforms.time > 36.0f) {
     // Fade out to black after 36 seconds
-    fade_amount = 1.0f - ((time - 36.0f) / 4.0f);
+    fade_amount = 1.0f - ((uniforms.time - 36.0f) / 4.0f);
     fade_amount = fmaxf(fade_amount, 0.0f);
   }