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, 2 insertions, 2 deletions

diff --git a/src/generated/test_demo_timeline.cc b/src/generated/test_demo_timeline.cc
index 75c5fe6..8b80d15 100644
--- a/src/generated/test_demo_timeline.cc
+++ b/src/generated/test_demo_timeline.cc
@@ -6,10 +6,10 @@ float GetDemoDuration() {
   return 16.000000f;
 }
 
-void LoadTimeline(MainSequence& main_seq, WGPUDevice device, WGPUQueue queue, WGPUTextureFormat format) {
+void LoadTimeline(MainSequence& main_seq, const GpuContext& ctx) {
   {
     auto seq = std::make_shared<Sequence>();
-    seq->add_effect(std::make_shared<FlashEffect>(device, queue, format), 0.0f, 16.0f, 0);
+    seq->add_effect(std::make_shared<FlashEffect>(ctx), 0.0f, 16.0f, 0);
     main_seq.add_sequence(seq, 0.0f, 0);
   }
 }