Widen ValidateSupportedHost to accept tenancy hosts (*.ghe.com) alongside
github.com. GHEC with data residency uses these domains, and all skill
subcommands (search, install, preview, publish, update) now allow them.
GitHub Enterprise Server remains unsupported and is explicitly rejected
with a clear error message.
Also fix the lockfile writer to use the actual host when constructing
SourceURL instead of hardcoding github.com.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
remove git sha because we only need git tree sha
remove github-owner from frontmatter, and make github-repo support full url. Only support github.com as host, error out otherwise
