Handed to the durable substrate; the caller must not also run it.
Not submitted — no submitter registered, or submission failed. The caller runs it inline.
Falling back rather than dropping is the whole posture: RunMode='Durable' asks for the work
to be harder to lose, so refusing to run it when the durable path is unavailable would make
the opt-in less reliable than leaving it off. The reason travels so the fallback is visible
in logs rather than looking like a binding that was never durable.
What a dispatch path did with a binding that asked for durability.