ci: skip ATOM Test for plugin-only PRs

[gyohuangxin]

Summary

• Skip native ATOM Test for plugin-only and plugin-test-only PRs.
• Route plugin-only PRs to the targeted plugin test workflow: SGLang-only changes run SGLang, vLLM-only changes run vLLM, and shared atom/plugin changes run both.
• Preserve full PR coverage for all other changes by letting native, vLLM, and SGLang tests all run when a PR includes any non-special path.

Routing

• atom/plugin/sglang/** only -> ATOM SGLang Test only.
• atom/plugin/vllm/** only -> ATOM vLLM Test only.
• shared atom/plugin/** only -> ATOM vLLM Test and ATOM SGLang Test.
• atom-sglang-* workflow or sglang_models_accuracy.json only -> ATOM SGLang Test only.
• atom-vllm-* workflow or oot_models_accuracy.json only -> ATOM vLLM Test only.
• Any mixed or other code path -> full native + vLLM + SGLang test coverage.

Test plan

• Ran git diff --check.
• Simulated representative paths-ignore cases locally for SGLang-only, vLLM-only, shared plugin, special workflow/config, and mixed/full-run changes.

[Copilot]

Pull request overview

Updates the ATOM Test GitHub Actions workflow to avoid running native test CI for pull requests that only touch plugin code under atom/plugin/**, reducing unnecessary CI load while keeping existing behavior for other PRs and for scheduled/manual runs.

Changes:

• Add atom/plugin/** to pull_request.paths-ignore in ATOM Test workflow so plugin-only PRs don’t trigger this workflow.

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[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.