- NpcVisual emits position_changed signal during _physics_process
- SimulationManager.synchronize_npc_position() writes active position
into SimNPC state on movement, arrival, and navigation failure
- WorldViewManager forwards position_changed and syncs before
despawn/reload
- SimNPC stores travel_target_position and has_travel_target as
versioned state; NPCStateRecord v2 persists them with v1 migration
- WorldViewManager.spawn_npc_visual() resumes travel for traveling NPCs
via SimulationManager.request_current_travel()
- WorldViewManager.despawn_npc_visual() syncs position before removal
- WorldViewManager.reload_npc_visual() spawns a visual from persisted
state without rerolling target selection
- tests/npc_visual_lifecycle_test.gd proves unload/reload preserves
action, target, reservation, position, RNG state, and checksum
- simulation_state_serialization_test adds legacy v1 NPC migration test
that does not invent an active travel target
