[FEATURE] Expose NPC.CurrentBuilding

[ifBars]

What would you like to see?

Add a read-only NPC.CurrentBuilding property returning S1API.Map.Building?.

Why would this help?

Location-aware dialogue, schedules, quests, and world mods need to know which enterable building currently contains an NPC. The native property still exists, but mods cannot access it through S1API.

Extra Context (Optional)

The original TODO's blocker is gone because S1API.Map.Building now wraps the native NPCEnterableBuilding. Keep this property read-only so native enter/exit methods retain lifecycle ownership.

[ifBars]

@Diffuin Open a PR to implement this small issue

[diffuin]

I opened #265