Re-enqueue eligible failed/cancelled/timed_out rows.

Each row goes through the same quota-gate + enqueue path as a direct POST /run so subscription semantics and attempt budgets are enforced identically. A row that's already running, succeeded, out of attempt budget, or over a Free org's included quota lands in skipped. A row whose environment can make nothing lands in unquotable, failed immediately rather than enqueued to fail slowly.