Adds step-security/harden-runner (v2.22.4, SHA-pinned) as the first step of
every job in the reusable and repo workflows, in egress-policy: audit mode.
Audit mode only records network, file and process activity; it blocks nothing.
Unsupported environments (containers, FreeBSD VM guests, ubuntu-slim) are
skipped by the action itself. Dependabot's github-actions group keeps the pin
current.