Use the unstable LiveKit transport type

UnstableLivekitTransport covers every shape a homeserver may advertise
while MSC4195 evolves: a LiveKit SFU `url`, a `livekit_service_url`, or
both. Switching to it means a service URL is no longer guaranteed, so the
remaining code that relies on one checks for it explicitly: delegation
probing skips transports without one, the connection map keys transports
by whichever URL they carry, and the OpenID flow rejects transports
without a service URL until the client-server API flow lands.

src/room/InCallView.tsx

@@ -699,7 +699,12 @@ export const InCallView: FC<InCallViewProps> = ({
               livekitAlias: connectionItem.livekitAlias,
               // TODO compute is local or tag it in the livekit room items already
               isLocal: undefined,
-              url: connectionItem.transport.livekit_service_url,
+              url:
+                // It should be relatively clear to the user which kind of URL
+                // this is, based on the scheme (ws:// vs. http://)
+                "url" in connectionItem.transport
+                  ? connectionItem.transport.url
+                  : connectionItem.transport.livekit_service_url,
             }))}
           />
         </>