Open existing agents from links and the CLI (#2324)

* feat(desktop): open existing agents from links

Register a stable agent deep link and route it through the existing Desktop window. Add a matching CLI command that resolves the local server and activates the requested agent without creating or messaging it.

* fix(desktop): recover agent link delivery

packages/desktop/src/agent-navigation.test.ts

@@ -0,0 +1,33 @@
+import { describe, expect, it } from "vitest";
+import { AgentNavigationInbox, parseAgentDeepLinkFromArgv } from "./agent-navigation.js";
+
+describe("desktop agent navigation", () => {
+  it("finds an agent deep link among Electron launch arguments", () => {
+    expect(
+      parseAgentDeepLinkFromArgv([
+        "/Applications/Paseo.app/Contents/MacOS/Paseo",
+        "--no-sandbox",
+        "paseo://h/server-1/agent/agent-2",
+      ]),
+    ).toEqual({ serverId: "server-1", agentId: "agent-2" });
+  });
+
+  it("holds navigation until the existing renderer is ready", () => {
+    const inbox = new AgentNavigationInbox();
+    const target = { serverId: "server-1", agentId: "agent-2" };
+
+    expect(inbox.deliverOrQueue(7, target)).toBeNull();
+    expect(inbox.windowReady(7)).toEqual(target);
+    expect(inbox.deliverOrQueue(7, target)).toEqual(target);
+  });
+
+  it("returns only the newest navigation queued during startup", () => {
+    const inbox = new AgentNavigationInbox();
+
+    inbox.deliverOrQueue(7, { serverId: "server-1", agentId: "agent-1" });
+    inbox.deliverOrQueue(7, { serverId: "server-1", agentId: "agent-2" });
+
+    expect(inbox.windowReady(7)).toEqual({ serverId: "server-1", agentId: "agent-2" });
+    expect(inbox.windowReady(7)).toBeNull();
+  });
+});