The ArmingCheckReply uORB queue was sized to 4 (ORB_QUEUE_LENGTH) while
ExternalChecks supports up to MAX_NUM_REGISTRATIONS (8) external modes,
each of which publishes a reply for every ArmingCheckRequest. With more
than 4 registered modes the replies from the 5th+ mode overwrote earlier
ones within a single request cycle, so those modes were flagged
"unresponsive" and silently failed to activate.
Increase ORB_QUEUE_LENGTH to 8 to match MAX_NUM_REGISTRATIONS, and add a
static_assert so the two limits cannot drift apart again.
Fixes#27271
Signed-off-by: Marko T <marko.tavcar@c-astral.com>