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, 0 deletions

diff --git a/src/tests/webgpu_test_fixture.h b/src/tests/webgpu_test_fixture.h
index 2c700a4..fd08276 100644
--- a/src/tests/webgpu_test_fixture.h
+++ b/src/tests/webgpu_test_fixture.h
@@ -4,6 +4,7 @@
 
 #pragma once
 
+#include "gpu/gpu.h"
 #include "platform/platform.h"
 
 // Shared test fixture for WebGPU tests
@@ -25,6 +26,7 @@ class WebGPUTestFixture {
   WGPUDevice device() const { return device_; }
   WGPUQueue queue() const { return queue_; }
   WGPUTextureFormat format() const { return WGPUTextureFormat_BGRA8Unorm; }
+  GpuContext ctx() const { return {device_, queue_, format()}; }
 
   // Check if fixture is ready
   bool is_initialized() const { return device_ != nullptr; }