The database layer already refuses to advance a top-level assignee's
task to in_review without requires_user_review=1 — the right
invariant. But the HTTP route caught nothing specific and returned a
bare 500, so the CEO prompt had to carry a paragraph of "the system
will demote any such task back to todo, but the cycle wastes a
heartbeat slot" prose to keep the model away from the error path.
Translate the guard to a 422 NO_REVIEWER_ON_TOP_LEVEL_TASK response
with an actionable hint and rewrite the prompt section to describe
the contract instead of begging the model to avoid the failure.
Also drop the residual skill-looping paragraph now that hires get
their default kit on approval.
ZacharyZhang-NY
dd8485b7e2