Lobby and game quality improvements

Clearer first-join guidance and focused SkyWars and BuildBattles fixes make it easier to choose a game and start playing.

• The lobby now gives all five games a distinctive selector, a short description and direct access from the Cookie Build menu.
• New-player guidance highlights Quick Play, direct game selection and the main community links without repeating on every connection.
• SkyWars now opens the correct kit selector on Java without changing the working Bedrock flow.
• BuildBattles recovers its spare arenas more reliably and supports a wider safe decoration palette.