Built-in gh no longer picks a host from GH_HOST or GH_REPO

What

When the GitHub CLI (gh) is missing, Claude Code can supply its own limited gh for gh api calls. This release tightens how that stand-in decides which GitHub host a request goes to.

• If GH_HOST or GH_REPO names a host other than the default, that variable is not used to pick a host in this session. A new message says to pass --hostname <host> on the command instead.
• GH_REPO no longer accepts a host in front of the repository. The error now says to set GH_REPO=OWNER/REPO or spell the repository out in the endpoint, and a host in GH_REPO that is not a plain host name causes an error.
• A host taken from a git remote now goes through a refusal check.
• The help Claude sees when a repository has no default remote now says the remote chosen names the host the request goes to, and that GH_HOST and a host in GH_REPO pick no other host.
• The help for --hostname <host> only mentions "as GH_HOST" in some cases; the text is now built when it is shown.

Why

If you rely on GH_HOST or a host in GH_REPO to reach a GitHub Enterprise server, those gh commands may now be refused. Add --hostname <host> to the command instead. Hosts are also no longer taken unchecked from repository remotes.