[Mustapha Jaber (mustjab)]

Summary

External Dawn API package CI currently exercises the built-in WebGPU EP, but not the shared-plugin registration and provider-option path.

• Extend the native host test to register the WebGPU plugin, select its device explicitly, and pass the host's dawnProcTable through AppendExecutionProvider_V2.
• Reuse the existing Windows package-mode CI runner and matching host/package artifacts to build both the core DLL and WebGPU plugin without configuring native Dawn.
• Validate GPU Abs inference with CPU fallback disabled, reject a missing proc table, and ensure unrelated plugin-load failures cannot falsely pass the negative test.
• Retain built-in host coverage and configure-time rejection of invalid API packages.

Fixes #33043.

Validation

Windows x64 Release:

• Rebuilt the updated external host and package-backed core DLL; built-in inference and missing-proc-table rejection passed.
• Built fresh package-backed core and plugin DLLs and verified the copied DLL hashes before runtime tests.
• Plugin inference validated all 60 output values and explicitly selected the registered WebGPU EP.
• Missing-proc-table rejection and invalid-plugin-path rejection passed.
• Workflow parsing, built-in-before-plugin step ordering, scoped lint, whitespace checks, and editor diagnostics passed.

Other native platforms have not been validated locally.

[Copilot]

Copilot review overview

🟢 Approval recommended

No actionable issues were found in the plugin integration, negative-test handling, or CI ordering.

Review effort: Balanced
Findings: None

What changed in this PR

Adds Windows CI coverage for external Dawn API packages with the WebGPU plugin, addressing #33043 while retaining built-in coverage.

Changes:

• Registers and explicitly selects the plugin, forwarding the host’s dawnProcTable.
• Builds package-backed core and plugin DLLs and runs inference and rejection tests.
• Prevents unrelated plugin-load failures from passing the missing-proc-table test.

File	Description
onnxruntime/​test/​webgpu/​external_dawn/​main.cc	Adds plugin selection and stricter negative-test handling.
.github/​workflows/​windows_webgpu.yml	Adds package-backed plugin builds and runtime tests.

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