hark-store: rebuild cache on inconsistency, instead of crashing
hark-store: rebuild cache on inconsistency, instead of crashing

Addresses #4201, although the root cause of the cache inconsistency is
still at large.

urbit/urbit,ngzax/urbit,urbit/urbit,urbit/urbit,urbit/urbit,ngzax/urbit,urbit/urbit,ngzax/urbit,urbit/urbit,ngzax/urbit,ngzax/urbit,ngzax/urbit,ngzax/urbit,urbit/urbit