Detach subagents without archiving them (#1612)

* Add detach action for subagents

* Translate detached subagent connection error

* Address subagent detach review feedback

* Fix subagent integration test import

* Focus detached subagents as tabs

packages/protocol/src/messages.test.ts

@@ -2,6 +2,8 @@ import { describe, expect, test } from "vitest";
 import {
   FileExplorerRequestSchema,
   PaseoWorktreeArchiveRequestSchema,
+  parseServerInfoStatusPayload,
+  SessionInboundMessageSchema,
   SessionOutboundMessageSchema,
 } from "./messages.js";
 
@@ -131,6 +133,51 @@ describe("workspace descriptor message compatibility", () => {
   });
 });
 
+describe("agent detach RPC", () => {
+  test("parses the namespaced detach request", () => {
+    const parsed = SessionInboundMessageSchema.parse({
+      type: "agent.detach.request",
+      agentId: "child-agent",
+      requestId: "req-detach",
+    });
+
+    expect(parsed).toEqual({
+      type: "agent.detach.request",
+      agentId: "child-agent",
+      requestId: "req-detach",
+    });
+  });
+
+  test("parses the namespaced detach response", () => {
+    const parsed = SessionOutboundMessageSchema.parse({
+      type: "agent.detach.response",
+      payload: {
+        requestId: "req-detach",
+        agentId: "child-agent",
+        accepted: true,
+        error: null,
+      },
+    });
+
+    expect(parsed.type).toBe("agent.detach.response");
+  });
+
+  test("parses the agentDetach server feature gate", () => {
+    const parsed = parseServerInfoStatusPayload({
+      status: "server_info",
+      serverId: "srv-test",
+      features: {
+        agentDetach: true,
+      },
+    });
+
+    if (!parsed) {
+      throw new Error("Expected server info payload to parse");
+    }
+    expect(parsed.features?.agentDetach).toBe(true);
+  });
+});
+
 describe("file explorer request compatibility", () => {
   test("acceptBinary is optional for old clients and accepted for new clients", () => {
     expect(