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, 3 insertions, 4 deletions

diff --git a/src/gpu/effects/passthrough_effect.cc b/src/gpu/effects/passthrough_effect.cc
index 7825c0a..203f912 100644
--- a/src/gpu/effects/passthrough_effect.cc
+++ b/src/gpu/effects/passthrough_effect.cc
@@ -5,14 +5,13 @@
 #include "gpu/gpu.h"
 
 // --- PassthroughEffect ---
-PassthroughEffect::PassthroughEffect(WGPUDevice device, WGPUQueue queue,
-                                     WGPUTextureFormat format)
-    : PostProcessEffect(device, queue) {
+PassthroughEffect::PassthroughEffect(const GpuContext& ctx)
+    : PostProcessEffect(ctx) {
   uniforms_ =
       gpu_create_buffer(device_, sizeof(float) * 6,
                         WGPUBufferUsage_Uniform | WGPUBufferUsage_CopyDst);
   pipeline_ =
-      create_post_process_pipeline(device_, format, passthrough_shader_wgsl);
+      create_post_process_pipeline(device_, format_, passthrough_shader_wgsl);
 }
 void PassthroughEffect::update_bind_group(WGPUTextureView input_view) {
   struct {