test_demo: Add beat-synchronized CNN post-processing with version selection

- Add --cnn-version <1|2> flag to select between CNN v1 and v2
- Implement beat_phase modulation for dynamic blend in both CNN effects
- Fix CNN v2 per-layer uniform buffer sharing (each layer needs own buffer)
- Fix CNN v2 y-axis orientation to match render pass convention
- Add Scene1Effect as base visual layer to test_demo timeline
- Reorganize CNN v2 shaders into cnn_v2/ subdirectory
- Update asset paths and documentation for new shader organization

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

1 files changed, 7 insertions, 0 deletions

diff --git a/src/gpu/effects/cnn_effect.h b/src/gpu/effects/cnn_effect.h
index 1c9f0f3..3e2b7ca 100644
--- a/src/gpu/effects/cnn_effect.h
+++ b/src/gpu/effects/cnn_effect.h
@@ -34,10 +34,17 @@ class CNNEffect : public PostProcessEffect {
     return layer_index_ == 0;
   }
 
+  void set_beat_modulation(bool enabled, float scale = 1.0f) {
+    beat_modulated_ = enabled;
+    beat_scale_ = scale;
+  }
+
  private:
   int layer_index_;
   int total_layers_;
   float blend_amount_;
+  bool beat_modulated_ = false;
+  float beat_scale_ = 1.0f;
   WGPUTextureView input_view_;
   WGPUTextureView original_view_;
   UniformBuffer<CNNLayerParams> params_buffer_;