When spawn() itself fails — EACCES on a helper that lost its execute
bit, as the 1.10.2 catalog install did on AB on 2026-10-04 — the child
emits 'error' with no 'exit' to follow. The handler reported the error
but left `child` set and scheduled nothing: the 250 ms eval loop then
kept reporting a misleading "No signal" over the dead child object, and
the listener was parked until a remount.
Null the child in the error handler and retry on the slow timer, the
way spl-listener already does (which is why SPL healed itself the
moment its binary was chmod +x'd, while Timers needed a remount). The
error report stays visible: the eval loop does not report while there
is no child.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
