Changes

Overhaul /xprate with per-skill rates and cleaner announcements

Adds per-skill XP rates (/xprate mining 5.3) that resolve max-wins
against the global rate, an implicit event flag, rejection of rates
below the configured baseline, and /xprate show with per-rate
durations and tab completion hints.

Admin notifications now show the sender as a hoverable @name with
their UUID in the hover instead of appending the UUID to the name;
the console copy keeps name (uuid). Skill names in messages come from
the display-cased Overhaul.Name locale keys.

Also lowercases skill name tab completion across commands and fixes
the outdated-server warning to name Minecraft 1.20.5.
 (commit: 980b6cb)