Remove unused multiplayer protocol types, script/wasmBinary/capabilities fields,
and onNearItem trigger. Implement portal requiresKey gate, fix onDayNight and
onTouch triggers to fire for all inventory items, and add gold-based trading
economy with NPC kill rewards and merchant purchasing.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>