CNN v2: Add mip-level support to runtime effect

Binary format v2 includes mip_level in header (20 bytes, was 16).
Effect reads mip_level and passes to static features shader via uniform.
Shader samples from correct mip texture based on mip_level.

Changes:
- export_cnn_v2_weights.py: Header v2 with mip_level field
- cnn_v2_effect.h: Add StaticFeatureParams, mip_level member, params buffer
- cnn_v2_effect.cc: Read mip_level from weights, create/bind params buffer, update per-frame
- cnn_v2_static.wgsl: Accept params uniform, sample from selected mip level

Binary format v2:
- Header: 20 bytes (magic, version=2, num_layers, total_weights, mip_level)
- Backward compatible: v1 weights load with mip_level=0

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

1 files changed, 7 insertions, 0 deletions

diff --git a/src/gpu/effects/cnn_v2_effect.h b/src/gpu/effects/cnn_v2_effect.h
index 28aec8c..47dedf5 100644
--- a/src/gpu/effects/cnn_v2_effect.h
+++ b/src/gpu/effects/cnn_v2_effect.h
@@ -47,6 +47,11 @@ private:
     float blend_amount;
   };
 
+  struct StaticFeatureParams {
+    uint32_t mip_level;
+    uint32_t padding[3];
+  };
+
   void create_textures();
   void create_pipelines();
   void load_weights();
@@ -55,6 +60,7 @@ private:
   // Static features compute
   WGPUComputePipeline static_pipeline_;
   WGPUBindGroup static_bind_group_;
+  WGPUBuffer static_params_buffer_;
   WGPUTexture static_features_tex_;
   WGPUTextureView static_features_view_;
 
@@ -75,5 +81,6 @@ private:
   float blend_amount_ = 1.0f;
   bool beat_modulated_ = false;
   float beat_scale_ = 1.0f;
+  uint32_t mip_level_ = 0;
   bool initialized_;
 };