protocol: hello carries five fields; the released client reads no serverName

Upstream's git HEAD appends serverName to server_installed, but the shipped
1.0.4 client (fabric-26.2) decodes exactly version/lastGen/interval/mode/
ticks and vanilla disconnects the player with "8 bytes extra" on the first
hello. Verified with javap on the release jar; the other three codecs match.
Drops the server-name option (a leftover key now only warns).

Claude-Session: https://claude.ai/code/session_011FePLXwBsCGLTzaSkk1Z6V

src/main/resources/config.yml

@@ -58,10 +58,6 @@ sync:
   # cache, otherwise it forgets what it already has and re-syncs on every join.
   hello-delay-ticks: 100
 
-# Optional stable name sent to clients. The client mod uses it to recognise this
-# server when it is reached under a different address. Leave empty to disable.
-server-name: ""
-
 # Per-world settings. Keys are Bukkit world names. Anything not listed uses
 # "default". `layers` controls what is rendered:
 #   auto     surface for worlds with a sky, cave layers for worlds with a ceiling