const PASSES: usize = 3;Expand description
Scan passes one boot allows before giving up on convergence.
A heal completes torn writes and rescans to re-measure what they
explain, and each pass strictly reduces the classes it heals, so the
second pass is the one that repairs. The last pass never heals, which
bounds a shape that does not settle and keeps the dirt-driven clearing
lane in [repair] reachable on every boot.