66318b6e's comment and test docstring both claimed PLN heard the polled-loop
stutter. He did not. The Foundry server was not running: port 8765 was
another project's http.server, established two steps after the fix landed.
The bug is real and of exactly the reported shape, and it stays fixed - but
attributing a fix to a symptom it did not cause is how a wrong diagnosis
becomes documentation, which is this morning's -inf-faders mistake again.
Both places now say where it came from. The commit message is history and is
left alone.

And check-mix's --arm table called an unarmed `Mix` route "not recorded, by
choice" while --mix blocks on precisely that. Two modes of one tool must not
disagree about the same route.