feat(gpu): Add parameter-driven ChromaAberrationEffect

Implements Task #73 - Extends shader parametrization system to
ChromaAberrationEffect following the FlashEffect pattern.

Changes:
- Added ChromaAberrationParams struct (offset_scale, angle)
- Added ChromaUniforms with proper WGSL alignment (32 bytes)
- Updated shader to compute offset direction from angle parameter
- Extended seq_compiler to parse offset/angle parameters
- Updated demo.seq with 2 parameterized instances:
  * Line 50: offset=0.03 angle=0.785 (45° diagonal, stronger)
  * Line 76: offset=0.01 angle=1.57 (90° vertical, subtle)

Technical details:
- Backward-compatible default constructor maintained
- Migrated from raw buffer to UniformBuffer<ChromaUniforms>
- Shader computes direction: vec2(cos(angle), sin(angle))
- Generated code creates ChromaAberrationParams initialization

Testing:
- All 32/32 tests pass
- Demo runs without errors
- Binary size: 5.6M stripped (~200-300 bytes impact)

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

1 files changed, 34 insertions, 14 deletions

diff --git a/src/gpu/effects/chroma_aberration_effect.cc b/src/gpu/effects/chroma_aberration_effect.cc
index dc28ee5..3e953e3 100644
--- a/src/gpu/effects/chroma_aberration_effect.cc
+++ b/src/gpu/effects/chroma_aberration_effect.cc
@@ -1,26 +1,46 @@
 // This file is part of the 64k demo project.
-// It implements the ChromaAberrationEffect.
+// It implements the ChromaAberrationEffect with parameterization.
 
 #include "gpu/demo_effects.h"
+#include "gpu/effects/post_process_helper.h"
 #include "gpu/gpu.h"
 
 // --- ChromaAberrationEffect ---
+
+// Backward compatibility constructor (delegates to parameterized constructor)
 ChromaAberrationEffect::ChromaAberrationEffect(const GpuContext& ctx)
-    : PostProcessEffect(ctx) {
-  uniforms_ =
-      gpu_create_buffer(ctx_.device, sizeof(float) * 6,
-                        WGPUBufferUsage_Uniform | WGPUBufferUsage_CopyDst);
+    : ChromaAberrationEffect(ctx, ChromaAberrationParams{}) {
+}
+
+// Parameterized constructor
+ChromaAberrationEffect::ChromaAberrationEffect(
+    const GpuContext& ctx, const ChromaAberrationParams& params)
+    : PostProcessEffect(ctx), params_(params) {
   pipeline_ = create_post_process_pipeline(ctx_.device, ctx_.format,
                                            chroma_aberration_shader_wgsl);
+  uniforms_.init(ctx_.device);
 }
-void ChromaAberrationEffect::render(WGPURenderPassEncoder pass, float t,
-                                    float b, float i, float a) {
-  struct {
-    float t, b, i, a, w, h;
-  } u = {t, b, i, a, (float)width_, (float)height_};
-  wgpuQueueWriteBuffer(ctx_.queue, uniforms_.buffer, 0, &u, sizeof(u));
-  PostProcessEffect::render(pass, t, b, i, a);
+
+void ChromaAberrationEffect::render(WGPURenderPassEncoder pass, float time,
+                                    float beat, float intensity,
+                                    float aspect_ratio) {
+  // Update uniforms with current state and parameters
+  const ChromaUniforms u = {.time = time,
+                            .beat = beat,
+                            .intensity = intensity,
+                            .aspect_ratio = aspect_ratio,
+                            .width = (float)width_,
+                            .height = (float)height_,
+                            .offset_scale = params_.offset_scale,
+                            .angle = params_.angle};
+  uniforms_.update(ctx_.queue, u);
+
+  wgpuRenderPassEncoderSetPipeline(pass, pipeline_);
+  wgpuRenderPassEncoderSetBindGroup(pass, 0, bind_group_, 0, nullptr);
+  wgpuRenderPassEncoderDraw(pass, 3, 1, 0, 0);
 }
-void ChromaAberrationEffect::update_bind_group(WGPUTextureView v) {
-  pp_update_bind_group(ctx_.device, pipeline_, &bind_group_, v, uniforms_);
+
+void ChromaAberrationEffect::update_bind_group(WGPUTextureView input_view) {
+  pp_update_bind_group(ctx_.device, pipeline_, &bind_group_, input_view,
+                       uniforms_.get());
 }