Add agent discovery workflow to .github/instructions (#60000)

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: heiskr

.github/instructions/all.instructions.md

@@ -29,3 +29,12 @@ When you create a pull request:
 3. Label with "llm-generated". 
 4. If an issue exists, include "fixes owner/repo#issue" or "towards owner/repo#issue" as appropriate. 
 5. Always create PRs in **draft mode** using `--draft` flag.
+
+## Accessing docs.github.com content programmatically
+
+When you need to read GitHub Docs, use these endpoints on `docs.github.com` in order of preference:
+
+1. `/llms.txt` — Start here. Returns a structured overview of the site with links to pagelist endpoints for each product version.
+2. `/api/pagelist/:lang/:version` — Returns a list of all pages for a given language and version (e.g., `/api/pagelist/en/free-pro-team@latest`). Use `/api/pagelist/versions` and `/api/pagelist/languages` for available options.
+3. `/api/search/v1?query=...&language=...&version=...&client_name=...` — Search docs content (e.g., `/api/search/v1?query=actions&language=en&version=free-pro-team@latest&client_name=copilot`).
+4. `/api/article/body?pathname=...` — Returns the rendered markdown body of a page. Handles all page types including REST, GraphQL, and webhook reference pages.