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>

6 files changed, 14 insertions, 2 deletions

diff --git a/workspaces/main/shaders/cnn_v2_compute.wgsl b/workspaces/main/shaders/cnn_v2/cnn_v2_compute.wgsl
index b19a692..1e1704d 100644
--- a/workspaces/main/shaders/cnn_v2_compute.wgsl
+++ b/workspaces/main/shaders/cnn_v2/cnn_v2_compute.wgsl
@@ -9,6 +9,7 @@ struct LayerParams {
   out_channels: u32,
   weight_offset: u32,     // Offset in f16 units
   is_output_layer: u32,   // 1 if final layer (sigmoid), 0 otherwise (relu)
+  blend_amount: f32,      // [0,1] blend with original
 }
 
 @group(0) @binding(0) var static_features: texture_2d<u32>;       // 8-channel static features
@@ -16,6 +17,7 @@ struct LayerParams {
 @group(0) @binding(2) var output_tex: texture_storage_2d<rgba32uint, write>;  // Current layer output
 @group(0) @binding(3) var<storage, read> weights_buffer: array<u32>;  // Packed f16 weights
 @group(0) @binding(4) var<uniform> params: LayerParams;
+@group(0) @binding(5) var original_input: texture_2d<f32>;        // Original RGB input for blending
 
 fn unpack_static_features(coord: vec2<i32>) -> array<f32, 8> {
   let packed = textureLoad(static_features, coord, 0);
@@ -133,5 +135,15 @@ fn main(@builtin(global_invocation_id) id: vec3<u32>) {
     output[c] = 0.0;
   }
 
+  // Blend with original on final layer
+  if (is_output) {
+    let original = textureLoad(original_input, coord, 0).rgb;
+    let result_rgb = vec3<f32>(output[0], output[1], output[2]);
+    let blended = mix(original, result_rgb, params.blend_amount);
+    output[0] = blended.r;
+    output[1] = blended.g;
+    output[2] = blended.b;
+  }
+
   textureStore(output_tex, coord, pack_channels(output));
 }
diff --git a/workspaces/main/shaders/cnn_v2_layer_0.wgsl b/workspaces/main/shaders/cnn_v2/cnn_v2_layer_0.wgsl
index 8e14957..8e14957 100644
--- a/workspaces/main/shaders/cnn_v2_layer_0.wgsl
+++ b/workspaces/main/shaders/cnn_v2/cnn_v2_layer_0.wgsl
diff --git a/workspaces/main/shaders/cnn_v2_layer_1.wgsl b/workspaces/main/shaders/cnn_v2/cnn_v2_layer_1.wgsl
index f490d13..f490d13 100644
--- a/workspaces/main/shaders/cnn_v2_layer_1.wgsl
+++ b/workspaces/main/shaders/cnn_v2/cnn_v2_layer_1.wgsl
diff --git a/workspaces/main/shaders/cnn_v2_layer_2.wgsl b/workspaces/main/shaders/cnn_v2/cnn_v2_layer_2.wgsl
index 2f9836a..2f9836a 100644
--- a/workspaces/main/shaders/cnn_v2_layer_2.wgsl
+++ b/workspaces/main/shaders/cnn_v2/cnn_v2_layer_2.wgsl
diff --git a/workspaces/main/shaders/cnn_v2_layer_template.wgsl b/workspaces/main/shaders/cnn_v2/cnn_v2_layer_template.wgsl
index 1bf6819..1bf6819 100644
--- a/workspaces/main/shaders/cnn_v2_layer_template.wgsl
+++ b/workspaces/main/shaders/cnn_v2/cnn_v2_layer_template.wgsl
diff --git a/workspaces/main/shaders/cnn_v2_static.wgsl b/workspaces/main/shaders/cnn_v2/cnn_v2_static.wgsl
index c3a2de7..dd07f19 100644
--- a/workspaces/main/shaders/cnn_v2_static.wgsl
+++ b/workspaces/main/shaders/cnn_v2/cnn_v2_static.wgsl
@@ -25,9 +25,9 @@ fn main(@builtin(global_invocation_id) id: vec3<u32>) {
   // Sample depth
   let d = textureLoad(depth_tex, coord, 0).r;
 
-  // UV coordinates (normalized [0,1])
+  // UV coordinates (normalized [0,1], bottom-left origin)
   let uv_x = f32(coord.x) / f32(dims.x);
-  let uv_y = f32(coord.y) / f32(dims.y);
+  let uv_y = 1.0 - (f32(coord.y) / f32(dims.y));
 
   // Multi-frequency position encoding
   let sin10_x = sin(10.0 * uv_x);