Carries the new column through create, PATCH, and bulk. Clearing is an
explicit clear_reasoning_effort flag rather than a null, because a null in a
PATCH body means "field not sent", not "set to NULL" — the same shape the
model override already uses, and the reason "none" can stay a real value.
Tests cover normalization, the depth-survives-a-model-clear invariant, both
spawn-argv branches, and the REST round-trip. One asserts the worker CLI
actually accepts the --reasoning flag the dispatcher emits: a spawn arg no
parser accepts would fail every dispatch while every unit test stayed green.
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