feat(subagent): durable child catalog and list_agents

Implements the durable-subagent-catalog RFC: SubagentControlService.listChildren()
enumerates a parent's direct continuable children from one sessionQuery trace,
validates each child's sole subagent/descriptor event (now carrying the durable
creation label), and returns one ordered SubagentListEntry[] with per-child
corrupt/unsupported/unavailable diagnostics. The list_agents tool ships as a
separately loadable plugin of dsh-tool-subagent-control requiring sessionQuery
at load; send_message stays usable without it.

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

@@ -896,6 +896,10 @@ export const SERVICE_API: readonly ServiceApiEntry[] = [
         signature: 'async drainContinuableDescendants(parents: readonly Agent[]): Promise<void>',
         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: 'registerProvider(provider: SubagentProvider): () => void',
         jsDoc: '/**\n * Register a provider under its name. Registration is effect-scoped and HMR\n * safe; removing a provider blocks new starts but does not revoke runs that\n * were already returned to their holders.\n * @param provider - the trusted provider implementation.\n * @returns the exact Cordis effect disposer.\n */',
@@ -1809,7 +1813,7 @@ export const TYPE_API: readonly TypeApiEntry[] = [
   },
   {
     name: 'ContinuableStartSpec',
-    declaration: 'export interface ContinuableStartSpec {\n    readonly provider: string;\n    readonly request: Omit<SubagentStartRequest, \'signal\' | \'outputSchema\'>;\n    readonly signal: AbortSignal;\n}',
+    declaration: 'export interface ContinuableStartSpec {\n    readonly provider: string;\n    readonly label: string;\n    readonly request: Omit<SubagentStartRequest, \'signal\' | \'outputSchema\'>;\n    readonly signal: AbortSignal;\n}',
   },
   {
     name: 'CreateAgentOptions',
@@ -2691,6 +2695,10 @@ export const TYPE_API: readonly TypeApiEntry[] = [
     name: 'SubagentFollowupOptions',
     declaration: 'export interface SubagentFollowupOptions {\n    readonly source: MessageSource;\n    readonly signal: AbortSignal;\n}',
   },
+  {
+    name: 'SubagentListEntry',
+    declaration: 'export type SubagentListEntry = {\n    readonly kind: \'child\';\n    readonly id: SessionId;\n    readonly label: string;\n    readonly status: \'running\' | \'complete\';\n} | {\n    readonly kind: \'diagnostic\';\n    readonly id: SessionId;\n    readonly reason: \'corrupt\' | \'unsupported\' | \'unavailable\';\n};',
+  },
   {
     name: 'SubagentProvider',
     declaration: 'export interface SubagentProvider {\n    readonly name: string;\n    readonly capabilities: SubagentCapabilities;\n    readonly inheritsParentContext: boolean;\n    start(request: SubagentStartRequest): Promise<SubagentRun>;\n    prepareContinuable?(request: ContinuableCreateRequest): Promise<ContinuableCreateSpec>;\n}',