fix: calculate beat_phase for FlashEffect and refactor uniforms

- seq_compiler.py: Calculate beat_phase from beat_time (was hardcoded 0.0f)
- Refactor: Replace CommonPostProcessUniforms with UniformsSequenceParams
- Remove duplicate struct definition in post_process_helper.h
- Update all CNN effects and tests to use unified uniform struct
- Fixes FlashEffect showing solid white instead of flashing to beat

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

1 files changed, 2 insertions, 2 deletions

diff --git a/tools/shadertoy/template.cc b/tools/shadertoy/template.cc
index 7636c0a..56b4ab5 100644
--- a/tools/shadertoy/template.cc
+++ b/tools/shadertoy/template.cc
@@ -83,7 +83,7 @@ void ShaderToyEffect::init(MainSequence* demo) {
       {.binding = 1, .textureView = prev_view},
       {.binding = 2,
        .buffer = uniforms_.get().buffer,
-       .size = sizeof(CommonPostProcessUniforms)},
+       .size = sizeof(UniformsSequenceParams)},
       {.binding = 3,
        .buffer = params_.get().buffer,
        .size = sizeof(ShaderToyParams)},
@@ -98,7 +98,7 @@ void ShaderToyEffect::init(MainSequence* demo) {
 
 void ShaderToyEffect::render(WGPURenderPassEncoder pass, float time, float beat,
                              float intensity, float aspect_ratio) {
-  const CommonPostProcessUniforms uniforms = {
+  const UniformsSequenceParams uniforms = {
       .resolution = {static_cast<float>(width_), static_cast<float>(height_)},
       .aspect_ratio = aspect_ratio,
       .time = time,