Lise

* Fix a crash when resuming ELiDE in the past of a simulation
* Fix rules sometimes not triggering, based on when the trigger was set

* Fix time travel via rule stepper
* Restore the ability to delete Characters
* Even faster interbranch time travel
* Fix a crash when time traveling between times with no changes to the world

* More crash fixes

* Crash fixes involving time travel
* Speed up interbranch time travel somewhat
* Switch to ruff formatter

* Fix another concurrency issue

* Automatically unload history, thus minimizing memory usage for long games
By default, this happens whenever you commit changes to the database.
* Improved support for ELiDE widgets in games
* New example sim, awareness.py, to demonstrate this
* Moved `game_start` into its own module
* Dropped support for Python 3.7 and the lz4 module
* A lot of fixes regarding thread safety and interprocess sync