TODO for Phase 3 (Simulation)

cars

model cars parking
- make vanished cars just park again, when possible
- when parking is full or no parking at goal road, roam until parking is found
code cleanup
- try to simplify straw_model step (less phases?)
- figure out responsibility btwn agents and managers, then fix up visibility
- rng should live in a scenario spec layer, not in the sim itself
better visualization
- draw moving / blocked colors (gradually more red as they wait longer)
- draw stop buffer in front/behind of cars
- draw cars in slightly different colors, to distinguish them better
start implementing a second AORTAish driving model
- then make cars park/unpark at the correct position
reversible sim

make them obey intersections (deterministically!)
make them start and end at buildings
- trim the sidewalk path to the edge of a building

savestating a sim has nondet output due to hashes; switching to btree is kind of weird
diffing two sim states is tedious no matter what; is there a nice macro-driven deep equals we could do instead?