intruder alerts

New

• Ignore list — server anti-cheat probe bots (e.g. MineProbe) no longer trigger alerts. Ships with MineProbe pre-configured; edit config/intruderalerts_ignore.json or use the new commands.
• Below-world-floor filter — any "player" with Y below world.getBottomY() (e.g. Y=-66 in overworld) is auto-skipped. Catches probe bots that change names per session.

New commands

• /intruder ignore add <name> — start ignoring a player name
• /intruder ignore remove <name> — stop ignoring
• /intruder ignore list — show all ignored names

Docs

• README now documents every command (the demo, history, history <player>, and history clear commands were already there but undocumented).