join_room and open_dm shared a fall-through case with
(fmtRoom(input.room) || fmtUser(input.user_id) || '?'). fmtRoom()
returns the string '?' when input.room is undefined — truthy — so
the fmtUser() fallback was never reached and open_dm always displayed
'open_dm* ?'.
Split into two separate cases: join_room reads input.room, open_dm
reads input.user_id. Both degrade to '?' via fmtRoom/fmtUser's own
null guard.
66057a97f7