Add per-player border color command

[tastybento]

Summary

• Adds /is border color <red|green|blue> (and standalone /is bordercolor) so players can set their own vanilla border color independently of the global config
• Each color is gated by a dedicated permission node: [gamemode].border.color.<color> (e.g. bskyblock.border.color.red)
  • Use [gamemode].border.color.* to get all of them
• Tab completion only shows the colors the player has permission to use
• ShowWorldBorder now reads the per-player color from metadata, falling back to the global config setting if none is set

Changes

File	What changed
BorderColorCommand	New command class
PerPlayerBorderProxy	Added BORDER_COLOR_META_DATA constant
ShowWorldBorder	Reads per-player color metadata before falling back to config
IslandBorderCommand	Registers color as a subcommand
Border	Registers standalone bordercolor command
en-US.yml	Adds set-color locale strings
BorderColorCommandTest	15 new tests covering all paths
IslandBorderCommandTest	Updated expected subcommand count (2 → 3)

Test plan

• All 86 tests pass (mvn test)
• /is border color red sets red border for the executing player only (others unaffected)
• Command is denied without bskyblock.border.color.red permission
• Tab completion shows only colors the player has permission for
• Falling back to global config color works when no per-player color is set

🤖 Generated with Claude Code

[sonarqubecloud]

Quality Gate failed

Failed conditions
4.2% Duplication on New Code (required ≤ 3%)

See analysis details on SonarQube Cloud