Now that the 2026-06-10 concurrency restructure makes concurrent recipe runs
safe (per-run trees, app-domain locks, isolation), default /upgrade-all to run
up to DRONE_RUNNER_CAPACITY (the drone runner's slots, currently 2) recipe
subagents at a time instead of strictly sequential — using all available
concurrency without oversubscribing. Query the live capacity from
'systemctl show drone-runner-exec' (fallback 2); process recipes in waves of
CAP (emit CAP Agent calls per message, await, next wave). Flags: --capacity N,
--sequential (CAP=1, old default — use when the build loops share the box),
--parallel (unbounded). Applies to the NEXT run; the in-flight run is unaffected.
a45517b432