CNN v2: Change feature #6 from sin(10*x) to sin(20*y)

Update positional encoding to use vertical coordinate at higher frequency.

Changes:
- train_cnn_v2.py: sin10_x → sin20_y (computed from uv_y)
- cnn_v2_static.wgsl: sin10_x → sin20_y (computed from uv_y)
- index.html: sin10_x → sin20_y (STATIC_SHADER)
- CNN_V2.md: Update feature descriptions and examples
- CNN_V2_BINARY_FORMAT.md: Update static features documentation

Feature vector: [p0, p1, p2, p3, uv_x, uv_y, sin20_y, bias]

Rationale: Higher frequency (20 vs 10) + vertical axis provides better
spatial discrimination for position encoding.

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

1 files changed, 2 insertions, 2 deletions

diff --git a/tools/cnn_v2_test/index.html b/tools/cnn_v2_test/index.html
index 88c4733..cab20ea 100644
--- a/tools/cnn_v2_test/index.html
+++ b/tools/cnn_v2_test/index.html
@@ -414,13 +414,13 @@ fn main(@builtin(global_invocation_id) id: vec3<u32>) {
   let d = textureLoad(depth_tex, coord, 0).r;
   let uv_x = f32(coord.x) / f32(dims.x);
   let uv_y = 1.0 - (f32(coord.y) / f32(dims.y));
-  let sin10_x = sin(10.0 * uv_x);
+  let sin20_y = sin(20.0 * uv_y);
 
   let packed = vec4<u32>(
     pack2x16float(vec2<f32>(rgba.r, rgba.g)),
     pack2x16float(vec2<f32>(rgba.b, d)),
     pack2x16float(vec2<f32>(uv_x, uv_y)),
-    pack2x16float(vec2<f32>(sin10_x, 1.0))
+    pack2x16float(vec2<f32>(sin20_y, 1.0))
   );
   textureStore(output_tex, coord, packed);
 }`;