Agent Skills: lisa-github-read-issue

Fetches the full scope of a GitHub Issue — metadata, body sections, all comments, native sub-issue parent and children, linked PRs, related issues parsed from `Blocks/Blocked by/Relates to/Duplicates/Cloned from` lines, and any cross-repo references. Produces a consolidated context bundle that downstream agents consume so they never act on an issue in isolation. The GitHub counterpart of lisa-jira-read-ticket.