[WIP] Fix URL path issue in learning hub (#895)

* Initial plan

* fix: use relative links in learning-hub index to preserve base path

Co-authored-by: aaronpowell <434140+aaronpowell@users.noreply.github.com>

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: aaronpowell <434140+aaronpowell@users.noreply.github.com>

Author: Copilot

website/src/content/docs/learning-hub/index.md

@@ -16,17 +16,17 @@ tableOfContents: false
 ## Fundamentals
 
 Essential concepts to tailor GitHub Copilot beyond its default experience. Start with
-[What are Agents, Skills, and Instructions](/learning-hub/what-are-agents-skills-instructions/)
+[What are Agents, Skills, and Instructions](what-are-agents-skills-instructions/)
 and work through the full track to master every customization primitive.
 
 ## Reference
 
 Quick-lookup resources to keep handy while you work. Browse the
-[GitHub Copilot Terminology Glossary](/learning-hub/github-copilot-terminology-glossary/)
+[GitHub Copilot Terminology Glossary](github-copilot-terminology-glossary/)
 for definitions of common terms and concepts.
 
 ## Hands-on
 
 Interactive samples and recipes to learn by doing. Jump into the
-[Cookbook](/learning-hub/cookbook/) for code samples, recipes,
+[Cookbook](cookbook/) for code samples, recipes,
 and examples you can use right away.