test(server): reproduce missed cross-client agent deletion

Retain the failing reproduction for #4870. Deletion reaches the requesting subscription but leaves other connected agent subscriptions stale. No production behavior is changed.

packages/server/src/server/daemon-e2e/agent-deletion-broadcast.e2e.test.ts

@@ -0,0 +1,57 @@
+import { expect, test } from "vitest";
+import { createDaemonTestContext } from "../test-utils/index.js";
+import { DaemonClient } from "../test-utils/daemon-client.js";
+import type { SessionOutboundMessage } from "../messages.js";
+
+test("deleting an agent removes it from every connected agent subscription", async () => {
+  const ctx = await createDaemonTestContext();
+  const observer = new DaemonClient({ url: `ws://127.0.0.1:${ctx.daemon.port}/ws` });
+  const updates: SessionOutboundMessage[] = [];
+  const requestorUpdates: SessionOutboundMessage[] = [];
+  try {
+    await observer.connect();
+    const agent = await ctx.client.createAgent({
+      provider: "codex",
+      cwd: ctx.daemon.staticDir,
+      title: "Cross-client deletion",
+    });
+    const snapshot = await observer.fetchAgents({ subscribe: {} });
+    expect(snapshot.entries.some((entry) => entry.agent.id === agent.id)).toBe(true);
+    observer.subscribeRawMessages((message) => updates.push(message));
+    ctx.client.subscribeRawMessages((message) => requestorUpdates.push(message));
+
+    await ctx.client.deleteAgent(agent.id);
+
+    // The record is gone, and a fresh query sees that. An existing subscriber
+    // must learn the same fact without reconnecting or fetching another list.
+    const afterDelete = await ctx.client.fetchAgents();
+    expect(afterDelete.entries.some((entry) => entry.agent.id === agent.id)).toBe(false);
+    expect(
+      requestorUpdates.some(
+        (message) =>
+          message.type === "agent_update" &&
+          message.payload.kind === "remove" &&
+          message.payload.agentId === agent.id,
+      ),
+    ).toBe(true);
+    await expect(observer.fetchAgentTimeline(agent.id, { direction: "tail" })).rejects.toThrow(
+      "Agent not found",
+    );
+
+    await expect
+      .poll(
+        () =>
+          updates.some(
+            (message) =>
+              message.type === "agent_update" &&
+              message.payload.kind === "remove" &&
+              message.payload.agentId === agent.id,
+          ),
+        { timeout: 2_000 },
+      )
+      .toBe(true);
+  } finally {
+    await observer.close();
+    await ctx.cleanup();
+  }
+});