Hologram Lines

/npc lines add adds floating text above an NPC. The remove, list and clear operations use the same ordered-list model as actions. Color codes can be used in displayed text where supported by the server renderer.

Keep the number and length of lines reasonable on hubs with many NPCs. If lines remain after deleting an NPC, confirm the delete completed and restart once so persisted NPC state is reconciled. Overlapping holograms normally mean NPCs are too close or have too many lines, not that the text was duplicated in storage.