The state-machine fixtures bound BOT1/BOT2/BOT3 to REQUIRED_BOTS by index off
the shipped .github/labels.conf, so three fixtures silently required a
four-member panel=. Shrinking it to three left the third slot unbound and
set -u aborted the file before assertion 1: 217 assertions became 0, on main
and on every branch cut from it.
The fixtures now write their own conf, in test/labels.test.sh's shape, at all
three load sites (top of file, the #205 re-drafted-round block, and the
mutant_blockers subshell). One live-file case survives as a property — the
shipped conf parses and recuses each member from its own panel — with no
index and no expected size, and a copy whose panel= names nobody proves it
still has teeth.
Refs #304
