* Add multiplayer, cloud sync, crash reporting, scene player, and memories features
* Fix multiplayer overlay showing "Waiting for ..." with no names
* Fix OGL link in README
* Update README with architecture, backend setup, environment variables, and CI docs
* Fix save editor showing wrong name for orphaned save slots
Players.gsi could fall out of sync with save files during cloud sync
because the saveSlotWritten event only tracked the slot file and
History.gsi for incremental upload, not Players.gsi. This caused
slots without a matching Players.gsi entry to display the first
player's name due to a fallback to index 0.
- Track Players.gsi in saveSlotWritten handler for incremental uploads
- Remove broken fallback to player index 0 in name resolution
- Hide save slots with no Players.gsi entry from the save editor UI
