Address PR review feedback
- generate_mul_model.py: use a single import style for onnx (CodeQL).
- WebGpuEp.cs: use ProcessArchitecture instead of OSArchitecture so emulated processes pick the matching native asset.
- README.md: simplify the usage example and note that error handling is omitted for readability.
- plugin-webgpu-nuget-packaging-stage.yml: drop the unused cmake_build_type parameter; compare templated booleans case-insensitively.
- WebGpuEpNuGetTest.csproj: add an OrtWebGpuPackageVersion property (default *-* for local dev) and reference it from PackageReference.
- plugin-win-webgpu-test-stage.yml: extract the exact package version from the .nupkg filename and pass it through to dotnet build via -p:OrtWebGpuPackageVersion; switch dotnet build/run steps to powershell with backtick continuations.
