The README's capability table is a measurement with a date on it, and a
runner upgrade or a gitea bump can invalidate it without anything saying
so. Committing the workflow that produced it means the next person can
re-derive the claims instead of trusting them, which is the same posture
the training probes take.
Carries the three job shapes plus the traps each one cost to find: job
images need a node binary or the first `uses:` fails, the Postgres service
needed ~6s and a pg_isready wait, and a run must be polled at
/actions/runs because /actions/tasks reports it as empty on 1.26.1.
Requested by vastblue-dev as a reference for their first smoke.
