archive(cnn): move CNN v1 to cnn_v1/ subdirectory

Consolidate CNN v1 (CNNEffect) into dedicated directory:
- C++ effect: src/effects → cnn_v1/src/
- Shaders: workspaces/main/shaders/cnn → cnn_v1/shaders/
- Training: training/train_cnn.py → cnn_v1/training/
- Docs: doc/CNN*.md → cnn_v1/docs/

Updated all references:
- CMake source list
- C++ includes (relative paths: ../../cnn_v1/src/)
- Asset paths (../../cnn_v1/shaders/)
- Documentation cross-references

CNN v1 remains active in timeline. For new work, use CNN v2 with
enhanced features (7D static, storage buffer, sigmoid activation).

Tests: 34/34 passing (100%)

1 files changed, 53 insertions, 0 deletions

diff --git a/cnn_v1/src/cnn_effect.h b/cnn_v1/src/cnn_effect.h
new file mode 100644
index 0000000..cdcd656
--- /dev/null
+++ b/cnn_v1/src/cnn_effect.h
@@ -0,0 +1,53 @@
+// CNN post-processing effect header
+// Multi-layer neural network stylization
+
+#pragma once
+#include "gpu/effect.h"
+#include "gpu/uniform_helper.h"
+
+struct CNNLayerParams {
+  int layer_index;
+  float blend_amount; // Blend: mix(input, output, blend_amount)
+  float _pad[2];
+};
+static_assert(sizeof(CNNLayerParams) == 16);
+
+struct CNNEffectParams {
+  int layer_index = 0;       // Which layer to render (0-based)
+  int total_layers = 1;      // Total number of layers in the CNN
+  float blend_amount = 1.0f; // Final blend with original input
+};
+
+class CNNEffect : public PostProcessEffect {
+ public:
+  explicit CNNEffect(const GpuContext& ctx);
+  explicit CNNEffect(const GpuContext& ctx, const CNNEffectParams& params);
+
+  void init(MainSequence* demo) override;
+  void resize(int width, int height) override;
+  void render(WGPURenderPassEncoder pass,
+              const CommonPostProcessUniforms& uniforms) override;
+  void update_bind_group(WGPUTextureView input_view) override;
+
+  // Layer 0 needs framebuffer capture for original input
+  bool needs_framebuffer_capture() const override {
+    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_;
+  WGPUBindGroup bind_group_;
+  MainSequence* demo_ = nullptr;
+};