CNN v2: bilinear mip-level sampling and UI improvements

**CNN v2 Changes:**
- Replace point sampling with bilinear interpolation for mip-level features
- Add linear sampler (binding 6) to static features shader
- Update CNNv2Effect, cnn_test, and HTML tool

**HTML Tool UI:**
- Move controls to floating bottom bar in central view
- Consolidate video controls + Blend/Depth/Save PNG in single container
- Increase left panel width: 300px → 315px (+5%)
- Remove per-frame debug messages (visualization, rendering logs)

**Technical:**
- WGSL: textureSample() with linear_sampler vs textureLoad()
- C++: Create WGPUSampler with Linear filtering
- HTML: Change sampler from 'nearest' to 'linear'

handoff(Claude): CNN v2 now uses bilinear mip-level sampling across all tools

1 files changed, 25 insertions, 5 deletions

diff --git a/tools/cnn_test.cc b/tools/cnn_test.cc
index c504c3d..b4a4bdc 100644
--- a/tools/cnn_test.cc
+++ b/tools/cnn_test.cc
@@ -784,6 +784,20 @@ static bool process_cnn_v2(WGPUDevice device, WGPUQueue queue,
   wgpuQueueWriteBuffer(queue, static_params_buffer, 0, &static_params,
                        sizeof(static_params));
 
+  // Create linear sampler for bilinear interpolation
+  WGPUSamplerDescriptor linear_sampler_desc = {};
+  linear_sampler_desc.addressModeU = WGPUAddressMode_ClampToEdge;
+  linear_sampler_desc.addressModeV = WGPUAddressMode_ClampToEdge;
+  linear_sampler_desc.addressModeW = WGPUAddressMode_ClampToEdge;
+  linear_sampler_desc.magFilter = WGPUFilterMode_Linear;
+  linear_sampler_desc.minFilter = WGPUFilterMode_Linear;
+  linear_sampler_desc.mipmapFilter = WGPUMipmapFilterMode_Linear;
+  linear_sampler_desc.lodMinClamp = 0.0f;
+  linear_sampler_desc.lodMaxClamp = 32.0f;
+  linear_sampler_desc.maxAnisotropy = 1;
+
+  WGPUSampler linear_sampler = wgpuDeviceCreateSampler(device, &linear_sampler_desc);
+
   // Create static features compute pipeline
   WGPUShaderSourceWGSL static_wgsl = {};
   static_wgsl.chain.sType = WGPUSType_ShaderSourceWGSL;
@@ -796,8 +810,8 @@ static bool process_cnn_v2(WGPUDevice device, WGPUQueue queue,
       wgpuDeviceCreateShaderModule(device, &static_module_desc);
 
   // Bind group layout: 0=input, 1=input_mip1, 2=input_mip2, 3=depth, 4=output,
-  // 5=params
-  WGPUBindGroupLayoutEntry static_bgl_entries[6] = {};
+  // 5=params, 6=linear_sampler
+  WGPUBindGroupLayoutEntry static_bgl_entries[7] = {};
   static_bgl_entries[0].binding = 0;
   static_bgl_entries[0].visibility = WGPUShaderStage_Compute;
   static_bgl_entries[0].texture.sampleType = WGPUTextureSampleType_Float;
@@ -832,8 +846,12 @@ static bool process_cnn_v2(WGPUDevice device, WGPUQueue queue,
   static_bgl_entries[5].buffer.minBindingSize =
       sizeof(CNNv2StaticFeatureParams);
 
+  static_bgl_entries[6].binding = 6;
+  static_bgl_entries[6].visibility = WGPUShaderStage_Compute;
+  static_bgl_entries[6].sampler.type = WGPUSamplerBindingType_Filtering;
+
   WGPUBindGroupLayoutDescriptor static_bgl_desc = {};
-  static_bgl_desc.entryCount = 6;
+  static_bgl_desc.entryCount = 7;
   static_bgl_desc.entries = static_bgl_entries;
 
   WGPUBindGroupLayout static_bgl =
@@ -858,7 +876,7 @@ static bool process_cnn_v2(WGPUDevice device, WGPUQueue queue,
   wgpuPipelineLayoutRelease(static_pl);
 
   // Create static bind group (use input as all mips for simplicity)
-  WGPUBindGroupEntry static_bg_entries[6] = {};
+  WGPUBindGroupEntry static_bg_entries[7] = {};
   static_bg_entries[0].binding = 0;
   static_bg_entries[0].textureView = input_view;
   static_bg_entries[1].binding = 1;
@@ -872,10 +890,12 @@ static bool process_cnn_v2(WGPUDevice device, WGPUQueue queue,
   static_bg_entries[5].binding = 5;
   static_bg_entries[5].buffer = static_params_buffer;
   static_bg_entries[5].size = sizeof(CNNv2StaticFeatureParams);
+  static_bg_entries[6].binding = 6;
+  static_bg_entries[6].sampler = linear_sampler;
 
   WGPUBindGroupDescriptor static_bg_desc = {};
   static_bg_desc.layout = static_bgl;
-  static_bg_desc.entryCount = 6;
+  static_bg_desc.entryCount = 7;
   static_bg_desc.entries = static_bg_entries;
 
   WGPUBindGroup static_bg = wgpuDeviceCreateBindGroup(device, &static_bg_desc);