Function get_retryable_ids_by_course_id 

pub async fn get_retryable_ids_by_course_id(
    conn: &mut PgConnection,
    course_id: Uuid,
    limit: i64,
) -> ModelResult<Vec<Uuid>>

The course’s live rows a bulk retry can actually move: failed for good, and not held open by Suotar. Oldest first, capped by limit.

Deliberately only these. A row a retry always refuses keeps matching for as long as it exists, so letting one into the batch would spend a slot of the cap on it forever: a course holding limit of them could never retry anything again. count_submission_uncertain_by_course_id is what reports them.