EzCountdown

Added

• Placeholder formatted output regression tests - added unit coverage in EzCountdownPlaceholderExpansionUnitTest to verify %ezcountdown_<name>_formatted% honors display.time-format.hide-leading-zeros for both enabled and disabled configurations.
• Optional countdown start/end sounds - countdowns can now define sounds.start and sounds.end with Bukkit Sound enum names in countdowns.yml.
• GUI sound editors - the in-game editor now includes dedicated actions to configure and validate start/end sounds, including none to disable either sound.

Changed

• Runtime start/end flow - when a configured start/end sound is valid, EzCountdown now plays it to online players at countdown start/end alongside existing message, teleport, firework, and command actions.