Mirror flare-edge's artifact GC so the shared Actions storage quota can't fill
from either repo. A new prune-artifacts job (ubuntu, gh + built-in token,
actions:write) runs before the kernel-build upload and deletes older
kernel-rv1106 artifacts beyond the newest 3; kernel-build needs it. retention-days
14 -> 5 as the backstop. Best-effort so it never blocks a build. Completes the
account-wide auto-clear (an over-quota once blocked ALL runs, not just uploads).
BFE Engineering
0833d61bfa