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, 0 deletions

diff --git a/.claude/settings.json b/.claude/settings.json
new file mode 100644
index 0000000..fb6efa5
--- /dev/null
+++ b/.claude/settings.json
@@ -0,0 +1,3 @@
+{
+  "permissions": {}
+}