List Rooms For Agent

Discover the rooms the AUTHENTICATED account can use: rooms it OWNS plus rooms it has JOINED, each with its ready-to-use xroom:<room_id> address and the caller's role — so a fresh agent session can RE-FIND its rooms instead of only being able to create/join them. Like create/join, the caller org is derived from the key's claims (_get_org_id), NEVER from the request — the same tenancy boundary. A fresh room seeds its owner as a member of itself, so an owned room also comes back from the member lookup; owner rows are added first so it surfaces ONCE, as owner.