Update sources.toml when forking packages
- Add upstream_url and subtree_name to fork_result type
- Extract subtree name from fork URL (last path component)
- Automatically update sources.toml with fork entry containing:
- url: the user's fork URL
- upstream: original dev-repo URL from source package
- reason: "Forked from <handle>"
This ensures sync uses the correct URLs for forked packages.
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>