Hosting a world sometimes fails to come online (shows "server not running")

**What**

When you start hosting a world, it sometimes does not actually come online. You or the friends you invite see "This server currently is not running" at the world's address, even though you just started hosting. The cause was the client connecting to an unreliable relay address (the bare relay domain), whose DNS entry is not always present, so the connection failed. It is now fixed by connecting through your world's full address instead, which always resolves. Already fixed on the nightly build — please test that hosting reliably comes online.

**How to reproduce**

1. Start hosting a singleplayer world.
2. Ping or join the world at its shown address (or have an invited friend try).
3. Before the fix: hosting could fail and show "This server currently is not running", depending on the relay's DNS state at the time. (environment-dependent, unconfirmed on demand)

**What to expect**

Starting to host reliably brings the world online, and it is joinable at its address every time, regardless of relay DNS quirks.