feat(subagents): archive finished children and show native names

Keep native provider sessions intact while letting users clear completed children from the track. Persist dismissed provider child IDs so history replay does not restore them.

packages/client/src/daemon-client.ts

@@ -498,6 +498,10 @@ export type ProviderSubagentListPayload = Extract<
   SessionOutboundMessage,
   { type: "agent.provider_subagents.list.response" }
 >["payload"];
+export type ArchiveFinishedSubagentsPayload = Extract<
+  SessionOutboundMessage,
+  { type: "agent.subagents.archive_finished.response" }
+>["payload"];
 export type ProviderSubagentTimelinePayload = Extract<
   SessionOutboundMessage,
   { type: "agent.provider_subagents.timeline.get.response" }
@@ -2514,6 +2518,33 @@ export class DaemonClient {
     return payload;
   }
 
+  async archiveFinishedSubagents(
+    parentAgentId: string,
+    options: { requestId?: string; timeout?: number } = {},
+  ): Promise<ArchiveFinishedSubagentsPayload> {
+    const requestId = this.createRequestId(options.requestId);
+    const message = SessionInboundMessageSchema.parse({
+      type: "agent.subagents.archive_finished.request",
+      parentAgentId,
+      requestId,
+    });
+    const payload = await this.sendRequest({
+      requestId,
+      message,
+      timeout: options.timeout,
+      options: { skipQueue: true },
+      select: (response) =>
+        response.type === "agent.subagents.archive_finished.response" &&
+        response.payload.requestId === requestId
+          ? response.payload
+          : null,
+    });
+    if (payload.error) {
+      throw new Error(payload.error);
+    }
+    return payload;
+  }
+
   async fetchProviderSubagentTimeline(
     parentAgentId: string,
     subagentId: string,