Discover Organizations For Email Domain

Which organizations already represent the caller's work email domain — the create-organization step's request-to-join default reads this (TEA-509). Authed but deliberately unscoped: the caller has no organization yet. The domain derives from the verified token's email, never a client parameter, so the only names disclosed are those a verified mailbox on that domain already entitles the caller to see — no enumeration surface. Soft: a personal email is an empty answer, never an error.