Fix master agent model switch availability copy

tests/master-agent-message-queue.test.ts

@@ -176,6 +176,50 @@ test("master-agent 明确要求切快模型时直接更新 controls 并返回完
   assert.equal(reply?.senderLabel ?? "", "主Agent·gpt-5.4-mini");
 });
 
+test("master-agent 切换模型成功时不会因为当前在线账号为空就回报可用模型暂无", async () => {
+  await saveAiAccount({
+    accountId: "master-codex-offline-switch",
+    label: "主 GPT",
+    role: "primary",
+    provider: "master_codex_node",
+    displayName: "Mac 上的 Master Codex Node",
+    nodeId: "offline-master-node",
+    nodeLabel: "离线 Codex",
+    model: "gpt-5.4",
+    enabled: true,
+    setActive: true,
+    loginStatusNote: "用于离线主节点模型切换文案测试。",
+  });
+
+  const response = await POST(
+    await createAuthedRequest("master-agent", {
+      body: "把主agent模型换成gpt5.4-mini",
+    }),
+    { params: Promise.resolve({ projectId: "master-agent" }) },
+  );
+
+  assert.equal(response.status, 200);
+  const payload = (await response.json()) as {
+    ok: boolean;
+    task?: { taskId: string } | null;
+    masterReplyState?: "queued" | "running" | "completed" | null;
+  };
+  assert.equal(payload.ok, true);
+  assert.equal(payload.task ?? null, null);
+  assert.equal(payload.masterReplyState, "completed");
+
+  const controls = await getProjectAgentControls("master-agent", "17600003315");
+  assert.equal(controls?.modelOverride ?? null, "gpt-5.4-mini");
+
+  const state = await readState();
+  const masterProject = state.projects.find((project) => project.id === "master-agent");
+  const reply = masterProject?.messages.at(-1);
+  assert.ok(reply, "expected the master-agent offline switch reply to be persisted");
+  assert.match(reply?.body ?? "", /已把主 Agent 的当前主模型切到 gpt-5\.4-mini/);
+  assert.doesNotMatch(reply?.body ?? "", /当前可用模型：暂无/);
+  assert.match(reply?.body ?? "", /已登记\/可选模型：/);
+});
+
 test("master-agent 识别自然写法的模型名并切当前主模型", async () => {
   await saveAiAccount({
     accountId: "openai-main-switch",