forge_url() now checks active context domain first before falling back
to production_host. Bare IP addresses are skipped in the host heuristic.
Adds .cargo/config.toml for the sunbeam Gitea Cargo registry.
Convert the single binary crate into a Cargo workspace with two members:
sunbeam-sdk (library) and sunbeam (thin binary). Moves build.rs to the
SDK with adjusted .git/HEAD path for the nested layout.
