feat(sequence): port rotating_cube_effect to v2

- Add RotatingCubeEffectV2 with 3D rendering + depth buffer
- Create rotating_cube_v2.wgsl (hardcoded cube geometry)
- Simplified: no auxiliary mask texture dependency
- Declare depth node via NodeRegistry
- Update timeline_v2.seq rotating_cube sequence
- Add shader exports to shaders.{h,cc}
- All 36 tests passing

handoff(Claude): RotatingCube v2 complete, hybrid_3d next

1 files changed, 1 insertions, 0 deletions

diff --git a/workspaces/main/assets.txt b/workspaces/main/assets.txt
index fe15cdf..9d15213 100644
--- a/workspaces/main/assets.txt
+++ b/workspaces/main/assets.txt
@@ -35,6 +35,7 @@ SHADER_PARTICLE_COMPUTE, NONE, shaders/particle_compute.wgsl, "Particle Compute
 SHADER_PARTICLE_RENDER, NONE, shaders/particle_render.wgsl, "Particle Render Shader"
 SHADER_PARTICLE_COMPUTE_V2, NONE, shaders/particle_compute_v2.wgsl, "Particle Compute Shader V2"
 SHADER_PARTICLE_RENDER_V2, NONE, shaders/particle_render_v2.wgsl, "Particle Render Shader V2"
+SHADER_ROTATING_CUBE_V2, NONE, shaders/rotating_cube_v2.wgsl, "Rotating Cube Shader V2"
 SHADER_PASSTHROUGH, NONE, ../../common/shaders/passthrough.wgsl, "Passthrough Shader"
 SHADER_ELLIPSE, NONE, shaders/ellipse.wgsl, "Ellipse Shader"
 SHADER_PARTICLE_SPRAY_COMPUTE, NONE, shaders/particle_spray_compute.wgsl, "Particle Spray Compute"