fix: address codex review round 1

- listChildren() takes an optional AbortSignal and rechecks it after every
  un-signalled session-query await (the cold-resume cooperative-cancellation
  boundary); list_agents forwards exec.signal so the registry's drain of
  started tool bodies cannot block on a slow or large catalog.
- The list_agents description now presents running/complete as a stored-record
  snapshot and defers deliverability to send_message, matching the ownership-
  conflict semantics the service tests pin.

packages/cordis/tool-cordis/src/api-catalog.ts

@@ -897,8 +897,8 @@ export const SERVICE_API: readonly ServiceApiEntry[] = [
         jsDoc: '/**\n * Close continuable admission below exact live parent Agents, stop only their\n * visible descendant Activations synchronously, then await admitted scoped\n * materializations and release those forests child-first. The scoped cutoff\n * lasts until each exact parent leaves the registry; unrelated parent trees\n * remain live.\n * @param parents - exact host-owned parent Agents entering teardown.\n * @returns once every retained descendant Activation released its `AgentHandle`.\n * @throws an aggregate error after all scoped branches settle when any failed.\n */',
       },
       {
-        signature: 'async listChildren(parentSessionId: SessionId): Promise<SubagentListEntry[]>',
-        jsDoc: '/**\n * Enumerate one session\'s direct continuable children from the durable,\n * live-preferred corpus without loading or resuming an Agent. The lineage\n * trace supplies stable candidate order and live status; each candidate is\n * then inspected independently for exactly one supported descriptor in its\n * own suffix.\n * @param parentSessionId - parent whose direct children are listed.\n * @returns child and diagnostic entries in lineage-trace order.\n */',
+        signature: 'async listChildren(parentSessionId: SessionId, signal?: AbortSignal): Promise<SubagentListEntry[]>',
+        jsDoc: '/**\n * Enumerate one session\'s direct continuable children from the durable,\n * live-preferred corpus without loading or resuming an Agent. The lineage\n * trace supplies stable candidate order and live status; each candidate is\n * then inspected independently for exactly one supported descriptor in its\n * own suffix. Session-query reads take no signal, so cancellation is\n * cooperative: the scan rechecks `signal` after every un-signalled await and\n * stops between candidates instead of draining a slow or large catalog after\n * the caller has gone.\n * @param parentSessionId - parent whose direct children are listed.\n * @param signal - caller-owned cancellation observed between query awaits.\n * @returns child and diagnostic entries in lineage-trace order.\n */',
       },
       {
         signature: 'registerProvider(provider: SubagentProvider): () => void',