Interface Subworkflows

Fan-out declared as an action's spawn, read back as $subworkflows. forEach is GROQ producing one row per subworkflow (bound as $row); each row needs an identity the engine can adopt on re-entry (_key ?? _id ?? GDR id, or the value itself for a scalar row) or the spawn fails. definition resolves by stable name, ordered version desc unless pinned. with seeds each child's initial fields; context delivers extra parent-scope values into the child's $context. onExit governs only still-live children when the cohort's scope stops applying: 'detach' (default) lets them run to completion, 'abort' kills them recursively — always an authored choice, never automatic. Whether the PARENT may move at all is a separate gate over $subworkflows.