Internal: added docs/TEAM_GUESTS.md, the contract for guests on teams: the role and its grants, what a guest can open, the one invitation, the admins' pages, the admitters for each area, conversions and logging. The specification moved to docs/archive/TEAM_GUESTS_SPEC.md, and docs/plans/TEAM_GUESTS_HANDOFF.md lists the departures, the checks only a person can do and read-only queries for the owner. Invitation expiry is now stored and compared in UTC and shown as the day in the viewer's time zone.
Added the guests contract
Internal: docs/TEAM_GUESTS.md describes guests as built; the specification moved to docs/archive/ and the handoff is in docs/plans/.