fix: Release cached samplers before WGPU shutdown

SamplerCache singleton never released samplers, causing device to retain
references at shutdown. Add clear() method and call before fixture cleanup.

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

2 files changed, 12 insertions, 0 deletions

diff --git a/src/gpu/sampler_cache.h b/src/gpu/sampler_cache.h
index 0f012a8..5df3958 100644
--- a/src/gpu/sampler_cache.h
+++ b/src/gpu/sampler_cache.h
@@ -58,4 +58,11 @@ public:
     return {WGPUAddressMode_ClampToEdge, WGPUAddressMode_ClampToEdge,
             WGPUFilterMode_Linear, WGPUFilterMode_Linear, 1};
   }
+
+  void clear() {
+    for (auto& pair : cache_) {
+      wgpuSamplerRelease(pair.second);
+    }
+    cache_.clear();
+  }
 };
diff --git a/tools/cnn_test.cc b/tools/cnn_test.cc
index 4ce9637..fa4394f 100644
--- a/tools/cnn_test.cc
+++ b/tools/cnn_test.cc
@@ -281,6 +281,7 @@ int main(int argc, char** argv) {
   WGPUTexture input_texture =
       load_texture(device, queue, args.input_path, &width, &height);
   if (!input_texture) {
+    SamplerCache::Get().clear();
     fixture.shutdown();
     return 1;
   }
@@ -311,6 +312,7 @@ int main(int argc, char** argv) {
     if (pipeline_final) wgpuRenderPipelineRelease(pipeline_final);
     wgpuTextureViewRelease(input_view);
     wgpuTextureRelease(input_texture);
+    SamplerCache::Get().clear();
     fixture.shutdown();
     return 1;
   }
@@ -448,6 +450,7 @@ int main(int argc, char** argv) {
         wgpuBindGroupLayoutRelease(bgl);
         wgpuRenderPipelineRelease(pipeline_final);
         wgpuRenderPipelineRelease(pipeline_intermediate);
+        SamplerCache::Get().clear();
         fixture.shutdown();
         return 1;
       }
@@ -474,6 +477,7 @@ int main(int argc, char** argv) {
         wgpuBindGroupLayoutRelease(bgl);
         wgpuRenderPipelineRelease(pipeline_final);
         wgpuRenderPipelineRelease(pipeline_intermediate);
+        SamplerCache::Get().clear();
         fixture.shutdown();
         return 1;
       }
@@ -540,6 +544,7 @@ int main(int argc, char** argv) {
   wgpuRenderPipelineRelease(pipeline_final);
   wgpuTextureViewRelease(input_view);
   wgpuTextureRelease(input_texture);
+  SamplerCache::Get().clear();
   fixture.shutdown();
 
   return 0;