Start a questionnaire↔survey audit
Creates a questionnaire↔survey audit pinned to a saved content revision and starts survey.audit (detect only).
content_revision defaults to the current tip. 404 if that revision does not exist. Source is loaded from the pinned revision — do not send a free-form source body. Unsaved editor drafts are not a revision.
Re-running on the same saved revision is allowed. 409 audit_already_exists only while an audit is still running for that revision.
Returns 202 { data: audit } with workflow_id (detect World run). Subscribe via GET /v1/workflows/{workflow_id} and .../stream. Domain payloads do not include stream_url.
Newest-wins across revisions: a new POST replaces any active detect run for this survey (survey.audit:{surveyId}).