Non-participants (e.g. tournament organizers) viewing a tournament
match chat could see the chat auto-open correctly, but clicking the
back arrow to the room list left the chat invisible — the only way
back was to leave the route and return.
The match chat appears in chatContext.rooms via the SUBSCRIBE
response, which (unlike the initial-payload path that participants
go through) does not check room expiry on the skalop side. So an
organizer viewing an old match ends up with an expired room in
their rooms list. ChatView already handles this gracefully with a
read-only banner, but RoomList was filtering on
expiresAt > Date.now() and dropping it.
Cleanup in useChatRouteSync removes the room from chatContext.rooms
on navigation, so exempting the current route's chatCode from the
expiry filter only affects the page that subscribed to it.
