feat: add GitHub Actions Node.js runtime upgrade agent

[joshjohanning]

Add an agent that handles the full lifecycle of upgrading GitHub Actions JavaScript/TypeScript actions to newer Node runtime versions, including action.yml changes, major version bumps, CI workflow updates, documentation updates, and build validation.

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.

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Description

Adds a new agent (github-actions-node-upgrade.agent.md) that guides the upgrade of a GitHub Actions JavaScript/TypeScript action to a newer Node runtime version (e.g., node20 to node24).

With node20 deprecated on GitHub Actions runners, hundreds of actions need to migrate to node24. This agent provides a standardized, step-by-step workflow covering:

• Updating runs.using in action.yml
• Major version bump via npm version major
• CI workflow and documentation updates
• Build validation and incompatibility scanning
• Commit message and PR content generation

Complements the existing github-actions-expert agent, which focuses on general CI/CD security and best practices, while this agent targets a specific, repeatable upgrade task.

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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):

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Additional Notes

No paid services involved. This agent has been tested against multiple JavaScript actions (e.g. https://github.com/joshjohanning/azdo_commit_message_validator/pull/160) for the node20 to node24 migration.

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By submitting this pull request, I confirm that my contribution abides by the Code of Conduct and will be licensed under the MIT License.

[Copilot]

Pull request overview

Adds a new declarative agent that guides maintainers through upgrading a JavaScript/TypeScript GitHub Action to a newer Node runtime (e.g., node20 → node24), and registers it in the agents catalog.

Changes:

• Added github-actions-node-upgrade agent content with step-by-step upgrade workflow and validation guidance.
• Registered the new agent in docs/README.agents.md so it appears in the repo’s agent index.

Reviewed changes

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

File	Description
docs/README.agents.md	Adds the new agent entry to the public agents list (with install badges).
agents/github-actions-node-upgrade.agent.md	Introduces a new agent describing an end-to-end Node runtime upgrade process for GitHub Actions JS/TS actions.