Login claims the chair, writes a session ticket, and starts a background
service for discovery plus revision-based context sync. Password Realm
opens require --login (or CST_REALM_PASSWORD); --service/--service-stop
manage the resident agent.
Co-authored-by: Cursor <cursoragent@cursor.com>
Exchange enrolled certificates and Ed25519 challenge signatures so
same-Realm instances can authenticate each other after discovery.
Co-authored-by: Cursor <cursoragent@cursor.com>
