Resume the subagents that a restart cut

A subagent that runs when the daemon stops goes on at the next start.
work.json in the agent directory holds the names of the running
subagents: each start and each end of a run writes it whole, but the
stop of the daemon does not, so it names the runs that the stop cut. The
logs alone cannot tell this, because a stop can cut a run just after its
final reply.

At the start, the chat gets the note "The daemon restarted, cutting
NAMES; nothing was lost: go on.", and each cut subagent gets the same
text as a told message, so it goes on from its log with the view of now.
The note starts no turn, but the reports of the subagents do. A subagent
that cannot go on gets a failed report, and work.json then no longer
names it, so the next start does not try it again. A failed write of
work.json stops the agent, as a failed log write does.

Issue: b1ac698