fix: offhand-buffer hat swap and share display name (26.9.5)

lang/en_us.yml

@@ -19,6 +19,7 @@ iridium.hat_success: 'Swapped hand item with head equipment'
 iridium.hat_unsupported_version: 'Version {0} does not support !!hat (needs Minecraft 1.8+)'
 iridium.hat_need_rcon: '!!hat requires RCON enabled to read and swap item data'
 iridium.hat_query_failed: 'Failed to query player item data'
+iridium.hat_offhand_busy: 'Off-hand is occupied; clear it before using !!hat'
 iridium.head_help: 'Get one player head (optional player name, cooldown {0}s)'
 iridium.head_help_short: 'Get one player head (optional player name)'
 iridium.head_success: 'You received a head of {0}'