[ingvarch]

What changes

Seven cleanups from the design review. urga behaves the same, except that the
allocations a fault narrows to are now judged at the time of the model, like
the rest of the screen.

• The keys of the log toggles (s, t, w) are named once, and the toggle
  line asks for the same constants.
• The comments on the colors of the rows explain them in urga's own terms.
• The mark of a queued job is built with jobMark, on the queue screen and in
  the map of the jobs list, so marks and actions read one name.
• fetchList only called request: every caller now calls request, and
  fetchList is gone.
• allocationsPage.take takes the time of the model instead of the wall
  clock, and is off the list of clock readers.
• The comment about Nomad's zero timestamp sits above unixTime again.
• readPoolQueues reads the queue of every node pool that has one, for both
  the jobs list and the queue screen. The jobs list still fails the whole read
  when a pool fails; the queue screen still shows the other pools and keeps no
  read index of the jobs. The probe of the pool default stays.

Found along the way: no test said the pool default is asked only when no pool
has a queue. A test now does.

Issues

Closes #206

Checklist

• The test for this change was written first and failed
• make check is green
• The guide in docs/ is updated if users see a difference
• The title is a conventional commit: feat(ui): ..., fix(nomad): ...