Learning Hub: Agents and subagents

[aaronpowell]

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

New page on the learning hub about agents and subagents.

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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

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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 Learning Hub Fundamentals article explaining delegated subagents, and wires it into the Learning Hub navigation and cross-references so readers can discover it from existing agent documentation.

Changes:

• Introduces a new “Agents and Subagents” Learning Hub page covering mental models, VS Code usage, and Copilot CLI /fleet.
• Adds cross-links from existing Learning Hub pages (agents overview, glossary, fundamentals index, related articles).
• Updates the Starlight sidebar to include the new page in the Fundamentals track.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
website/src/content/docs/learning-hub/what-are-agents-skills-instructions.md	Links agents concept to the new agents/subagents delegation article.
website/src/content/docs/learning-hub/index.md	Adds a Fundamentals-track pointer to the new delegation/orchestration article.
website/src/content/docs/learning-hub/github-copilot-terminology-glossary.md	Extends glossary with “Subagent” and “Handoff”, and links to the new article.
website/src/content/docs/learning-hub/building-custom-agents.md	Adds the new article as a related reading item.
website/src/content/docs/learning-hub/agents-and-subagents.md	New article describing agent vs subagent mental model and launch patterns.
website/astro.config.mjs	Adds the new article into the “Fundamentals” sidebar ordering.