refactor: Bundle GPU context into GpuContext struct

- Created GpuContext struct {device, queue, format}
- Updated Effect/PostProcessEffect to take const GpuContext&
- Updated all 19 effect implementations
- Updated MainSequence.init() and LoadTimeline() signatures
- Updated generated timeline files
- Updated all test files
- Added gpu_get_context() accessor and fixture.ctx() helper

Fixes test_mesh.cc compilation error from g_device/g_queue/g_format conflicts.
All targets build successfully.

1 files changed, 1 insertions, 2 deletions

diff --git a/src/gpu/effects/theme_modulation_effect.h b/src/gpu/effects/theme_modulation_effect.h
index ac584e2..ad7322e 100644
--- a/src/gpu/effects/theme_modulation_effect.h
+++ b/src/gpu/effects/theme_modulation_effect.h
@@ -8,8 +8,7 @@
 
 class ThemeModulationEffect : public PostProcessEffect {
  public:
-  ThemeModulationEffect(WGPUDevice device, WGPUQueue queue,
-                        WGPUTextureFormat format);
+  ThemeModulationEffect(const GpuContext& ctx);
   void render(WGPURenderPassEncoder pass, float time, float beat,
               float intensity, float aspect_ratio) override;
   void update_bind_group(WGPUTextureView input_view) override;