v0.1.30-pre.73

preview: nothing a person can see changes in this one. Underneath it, ui's jvm tests now open
their database on a file as every host does, with a build check that refuses the next test
written the old way, and a cancelled session no longer runs on into a read of a database that
removing an account has just deleted - a latent defect closed on the test suite's evidence,
not a crash anyone has been seeing.

No migration of its own: schema stays at 22 as at pre.72, so an account this build opens still
needs pre.61 or newer. Going back below that drops you at the account picker as though the
account were gone.

Landed from pr-thimble, pull request 91628851 at tip baca8aa2, merge 7ef3e5c2. Fixes #6384ae5b.