feat(gpu): add SDF camera infrastructure and effect base class

Add unified camera system for SDF raymarching effects:
- CameraParams struct (80 bytes): inv_view matrix + FOV/near/far/aspect
- SDFEffect base class: manages camera uniform, provides update_camera() helpers
- camera_common.wgsl: getCameraRay(), position/forward/up/right extractors
- SDFTestEffect: working example with orbiting camera + animated sphere

Refactor effect headers:
- Extract class definitions from demo_effects.h to individual .h files
- Update includes in .cc files to use specific headers
- Cleaner compilation dependencies, faster incremental builds

Documentation:
- Add SDF_EFFECT_GUIDE.md with complete workflow
- Update ARCHITECTURE.md, UNIFORM_BUFFER_GUIDELINES.md
- Update EFFECT_WORKFLOW.md, CONTRIBUTING.md

Tests: 34/34 passing, SDFTestEffect validated

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/cmake/DemoSourceLists.cmake b/cmake/DemoSourceLists.cmake
index a54eb4b..d4cdd21 100644
--- a/cmake/DemoSourceLists.cmake
+++ b/cmake/DemoSourceLists.cmake
@@ -29,11 +29,11 @@ set(UTIL_SOURCES src/util/asset_manager.cc src/util/file_watcher.cc)
 # GPU sources (conditional: HEADLESS / STRIP_EXTERNAL / NORMAL)
 demo_set_conditional_sources(GPU_SOURCES
     # Headless mode: Functional stubs (timeline/audio work)
-    "src/gpu/headless_gpu.cc;src/gpu/demo_effects.cc;src/gpu/effect.cc;src/effects/heptagon_effect.cc;src/effects/particles_effect.cc;src/effects/passthrough_effect.cc;src/effects/moving_ellipse_effect.cc;src/effects/particle_spray_effect.cc;src/effects/gaussian_blur_effect.cc;src/effects/solarize_effect.cc;src/effects/scene1_effect.cc;src/effects/chroma_aberration_effect.cc;src/effects/vignette_effect.cc;src/effects/cnn_effect.cc;src/effects/cnn_v2_effect.cc;src/gpu/post_process_helper.cc;src/gpu/shaders.cc;src/effects/hybrid_3d_effect.cc;src/effects/flash_cube_effect.cc;src/effects/theme_modulation_effect.cc;src/effects/fade_effect.cc;src/effects/flash_effect.cc;src/gpu/shader_composer.cc;src/effects/circle_mask_effect.cc;src/effects/rotating_cube_effect.cc;src/gpu/texture_manager.cc;src/gpu/texture_readback.cc"
+    "src/gpu/headless_gpu.cc;src/gpu/demo_effects.cc;src/gpu/effect.cc;src/effects/heptagon_effect.cc;src/effects/particles_effect.cc;src/effects/passthrough_effect.cc;src/effects/moving_ellipse_effect.cc;src/effects/particle_spray_effect.cc;src/effects/gaussian_blur_effect.cc;src/effects/solarize_effect.cc;src/effects/scene1_effect.cc;src/effects/chroma_aberration_effect.cc;src/effects/vignette_effect.cc;src/effects/cnn_effect.cc;src/effects/cnn_v2_effect.cc;src/gpu/post_process_helper.cc;src/gpu/shaders.cc;src/effects/hybrid_3d_effect.cc;src/effects/flash_cube_effect.cc;src/effects/theme_modulation_effect.cc;src/effects/fade_effect.cc;src/effects/flash_effect.cc;src/gpu/shader_composer.cc;src/effects/circle_mask_effect.cc;src/effects/rotating_cube_effect.cc;src/gpu/texture_manager.cc;src/gpu/texture_readback.cc;src/effects/sdf_test_effect.cc"
     # Strip mode: Minimal GPU stubs only
     "src/gpu/stub_gpu.cc"
     # Normal mode: Full GPU implementation
-    "src/gpu/gpu.cc;src/gpu/effect.cc;src/effects/heptagon_effect.cc;src/effects/particles_effect.cc;src/effects/passthrough_effect.cc;src/effects/moving_ellipse_effect.cc;src/effects/particle_spray_effect.cc;src/effects/gaussian_blur_effect.cc;src/effects/solarize_effect.cc;src/effects/scene1_effect.cc;src/effects/chroma_aberration_effect.cc;src/effects/vignette_effect.cc;src/effects/cnn_effect.cc;src/effects/cnn_v2_effect.cc;src/gpu/post_process_helper.cc;src/gpu/shaders.cc;src/effects/hybrid_3d_effect.cc;src/effects/flash_cube_effect.cc;src/effects/theme_modulation_effect.cc;src/effects/fade_effect.cc;src/effects/flash_effect.cc;src/gpu/shader_composer.cc;src/effects/circle_mask_effect.cc;src/effects/rotating_cube_effect.cc;src/gpu/texture_manager.cc;src/gpu/texture_readback.cc"
+    "src/gpu/gpu.cc;src/gpu/effect.cc;src/effects/heptagon_effect.cc;src/effects/particles_effect.cc;src/effects/passthrough_effect.cc;src/effects/moving_ellipse_effect.cc;src/effects/particle_spray_effect.cc;src/effects/gaussian_blur_effect.cc;src/effects/solarize_effect.cc;src/effects/scene1_effect.cc;src/effects/chroma_aberration_effect.cc;src/effects/vignette_effect.cc;src/effects/cnn_effect.cc;src/effects/cnn_v2_effect.cc;src/gpu/post_process_helper.cc;src/gpu/shaders.cc;src/effects/hybrid_3d_effect.cc;src/effects/flash_cube_effect.cc;src/effects/theme_modulation_effect.cc;src/effects/fade_effect.cc;src/effects/flash_effect.cc;src/gpu/shader_composer.cc;src/effects/circle_mask_effect.cc;src/effects/rotating_cube_effect.cc;src/gpu/texture_manager.cc;src/gpu/texture_readback.cc;src/effects/sdf_test_effect.cc"
 )
 
 # 3D sources (conditional: HEADLESS / STRIP_EXTERNAL / NORMAL)