fix: make smoke test check all valid plugin.json paths

[Surya-5555]

Pull Request Checklist

• I have read and followed the CONTRIBUTING.md guidelines.
• I have read and followed the Guidance for submissions involving paid services.
• My contribution adds a new instruction, prompt, agent, skill, or workflow file in the correct directory.
• The file follows the required naming convention.
• The content is clearly structured and follows the example format.
• I have tested my instructions, prompt, agent, skill, or workflow with GitHub Copilot.
• I have run npm start and verified that README.md is up to date.
• I am targeting the staged branch for this pull request.

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Description

The install smoke test in eng/external-plugin-quality-gates.mjs hardcoded a single expected path for plugin.json (.github/plugin/plugin.json), but the validator accepts three valid paths: plugin.json (root), .github/plugin/plugin.json, and .plugin/plugin.json. This inconsistency caused any plugin using the root convention to always fail the smoke test. This fix updates the smoke test to check all three valid paths, consistent with the validator. Fixes #1873.

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Type of Contribution

• New instruction file.
• New prompt file.
• New agent file.
• New plugin.
• New skill file.
• New agentic workflow.
• Update to existing instruction, prompt, agent, plugin, skill, or workflow.
• Other (please specify): Bug fix in tooling — eng/external-plugin-quality-gates.mjs

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Additional Notes

Reported by @gregorycrist in issue #1873. The fix makes the smoke test consistent with the validator by checking all three accepted plugin.json locations.

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[Copilot]

Pull request overview

Note

Copilot was unable to run its full agentic suite in this review.

Updates the external plugin install smoke gate to recognize plugin manifests in multiple supported locations instead of a single hard-coded path.

Changes:

• Search for plugin.json in several candidate locations under the installed plugin directory.
• Treat “manifest not found” as a gate failure when none of the candidate locations exist.

Comments suppressed due to low confidence (1)

eng/external-plugin-quality-gates.mjs:243

• The failure message no longer reflects what was actually checked (multiple manifest candidate locations). For easier diagnosis, include which manifest paths were probed (or at least that plugin.json was not found in any supported location) in the output.

      return {
        status: "fail",
        output: `Plugin installed but expected files were missing at ${installedPluginPath}`,
      };

[Surya-5555]

Hey @aaronpowell, wanted to flag this for your review. The install smoke test in eng/external-plugin-quality-gates.mjs was hardcoding .github/plugin/plugin.json as the only valid path, but the validator (eng/external-plugin-validation.mjs) accepts three valid paths — plugin.json (root), .github/plugin/plugin.json, and .plugin/plugin.json. This caused any plugin using the root convention to always fail the smoke test even though the validator passed it. This was reported by @gregorycrist in #1873. The fix updates the smoke test to check all three paths consistently. Happy to hear any feedback!