TODO

✔ React UI
❌ Multiple rooms
✔ Send relevant entity URIs to client; cache and use instead of full transfer
✔ Forget remembered entities after a while
✔ Optimize informed and Packer::pack: don't use .map on immutables
✔ Optimize Damaging::tick
✔ Manual state sync
- ✔ Informed tracks seen entities (etc?), responsible for upgrading updates