Put in the log a link to the FAQ for the following common case - Error: Permission error: GitHub Actions is not permitted to create or approve pull requests #251

[dsyme]

(From githubnext/agentics#251)

Add a link to the FAQ in this emitted diagnostic

Warning: Failed to create pull request: GitHub Actions is not permitted to create or approve pull requests.
Error: Permission error: GitHub Actions is not permitted to create or approve pull requests

This is the relevant FAQ: https://github.github.com/gh-aw/reference/faq/#why-is-my-create-pull-request-workflow-failing-with-github-actions-is-not-permitted-to-create-or-approve-pull-requests

In general we should sprinkle links to the FAQ around more freely through the diagnostics if there are other similar links we can add sensibly.