Carrier is the existing kind-0 'cordn' field (app convention, NIP.md) — no new
kind. It now holds a coordinator *pointer* rather than only a URL.
- EditProfileForm: accepts nprofile / cordn.net link / npub / hex / http URL,
validates via parseCoordinatorInput, normalises a bare pointer to Cordn's
canonical add-link on save, and adds 'Use my coordinator'. Label -> Coordinator.
- NIP19Page: when the profile's cordn value parses as a pointer, render a
Coordinator row with a one-tap Add (sets the viewer's coordinator, with toast)
and an 'Open in Cordn' link; otherwise keep the old plain-link row.
- NIP.md: document the broadened cordn field (pointer formats + one-tap add).
- smoke test: now boots a real profile route too.