refactor(cnn): isolate CNN v2 to cnn_v2/ subdirectory

Move all CNN v2 files to dedicated cnn_v2/ directory to prepare for CNN v3 development. Zero functional changes.

Structure:
- cnn_v2/src/ - C++ effect implementation
- cnn_v2/shaders/ - WGSL shaders (6 files)
- cnn_v2/weights/ - Binary weights (3 files)
- cnn_v2/training/ - Python training scripts (4 files)
- cnn_v2/scripts/ - Shell scripts (train_cnn_v2_full.sh)
- cnn_v2/tools/ - Validation tools (HTML)
- cnn_v2/docs/ - Documentation (4 markdown files)

Changes:
- Update CMake source list to cnn_v2/src/cnn_v2_effect.cc
- Update assets.txt with relative paths to cnn_v2/
- Update includes to ../../cnn_v2/src/cnn_v2_effect.h
- Add PROJECT_ROOT resolution to Python/shell scripts
- Update doc references in HOWTO.md, TODO.md
- Add cnn_v2/README.md

Verification: 34/34 tests passing, demo runs correctly.

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

1 files changed, 0 insertions, 68 deletions

diff --git a/workspaces/main/shaders/cnn_v2/cnn_v2_layer_template.wgsl b/workspaces/main/shaders/cnn_v2/cnn_v2_layer_template.wgsl
deleted file mode 100644
index 1bf6819..0000000
--- a/workspaces/main/shaders/cnn_v2/cnn_v2_layer_template.wgsl
+++ /dev/null
@@ -1,68 +0,0 @@
-// CNN v2 Layer Template (placeholder for generated shaders)
-// This file documents the structure - actual layers generated by export script
-
-// Example: Layer 0 (1×1 kernel, 8→16 channels)
-// const KERNEL_SIZE: u32 = 1u;
-// const IN_CHANNELS: u32 = 8u;  // 7 features + bias
-// const OUT_CHANNELS: u32 = 16u;
-// const weights: array<f32, 128> = array(...);
-
-@group(0) @binding(0) var static_features: texture_2d<u32>;
-@group(0) @binding(1) var layer_input: texture_2d<u32>;  // Previous layer output
-@group(0) @binding(2) var output_tex: texture_storage_2d<rgba32uint, write>;
-
-fn unpack_static_features(coord: vec2<i32>) -> array<f32, 8> {
-  let packed = textureLoad(static_features, coord, 0);
-  let v0 = unpack2x16float(packed.x);
-  let v1 = unpack2x16float(packed.y);
-  let v2 = unpack2x16float(packed.z);
-  let v3 = unpack2x16float(packed.w);
-  return array<f32, 8>(v0.x, v0.y, v1.x, v1.y, v2.x, v2.y, v3.x, v3.y);
-}
-
-fn unpack_layer_channels(coord: vec2<i32>) -> array<f32, 8> {
-  let packed = textureLoad(layer_input, coord, 0);
-  let v0 = unpack2x16float(packed.x);
-  let v1 = unpack2x16float(packed.y);
-  let v2 = unpack2x16float(packed.z);
-  let v3 = unpack2x16float(packed.w);
-  return array<f32, 8>(v0.x, v0.y, v1.x, v1.y, v2.x, v2.y, v3.x, v3.y);
-}
-
-fn pack_channels(values: array<f32, 8>) -> vec4<u32> {
-  return vec4<u32>(
-    pack2x16float(vec2<f32>(values[0], values[1])),
-    pack2x16float(vec2<f32>(values[2], values[3])),
-    pack2x16float(vec2<f32>(values[4], values[5])),
-    pack2x16float(vec2<f32>(values[6], values[7]))
-  );
-}
-
-@compute @workgroup_size(8, 8)
-fn main(@builtin(global_invocation_id) id: vec3<u32>) {
-  let coord = vec2<i32>(id.xy);
-  let dims = textureDimensions(static_features);
-
-  if (coord.x >= i32(dims.x) || coord.y >= i32(dims.y)) {
-    return;
-  }
-
-  // Load static features (always available)
-  let static_feat = unpack_static_features(coord);
-
-  // Convolution loop (example for generated code)
-  // var output: array<f32, OUT_CHANNELS>;
-  // for (var c: u32 = 0u; c < OUT_CHANNELS; c++) {
-  //   var sum: f32 = 0.0;
-  //   for (var ky: i32 = -radius; ky <= radius; ky++) {
-  //     for (var kx: i32 = -radius; kx <= radius; kx++) {
-  //       let sample_coord = coord + vec2<i32>(kx, ky);
-  //       // Load static + prev layer, multiply weights, accumulate
-  //     }
-  //   }
-  //   output[c] = max(0.0, sum);  // ReLU
-  // }
-
-  // Placeholder output
-  textureStore(output_tex, coord, vec4<u32>(0u));
-}