feat(hermes-chat): show readiness banner when Hermes is missing or Gateway is down (#256)

- Surface a top-of-input warning banner on the chat page when:
  * Hermes Agent is not installed -> red 'go to dashboard' banner;
  * Gateway is not running -> amber banner with the same dashboard link.
- Disable the send button (with a contextual tooltip) so users no longer
  hit cryptic backend errors when their environment is not ready.
- Force-refresh the cached check_hermes status on chat mount so a freshly
  started Gateway is reflected immediately instead of waiting 30s.
- Add zh-CN/en/zh-TW copy + matching error/warn styling that reuses the
  existing Hermes color tokens.

src/engines/hermes/pages/chat.js

@@ -14,7 +14,7 @@
  * State lives in `chat-store.js`; this module only does DOM + events.
  */
 import { t } from '../../../lib/i18n.js'
-import { api } from '../../../lib/tauri-api.js'
+import { api, invalidate } from '../../../lib/tauri-api.js'
 import { toast } from '../../../components/toast.js'
 import { showConfirm } from '../../../components/modal.js'
 import { getChatStore, getSourceLabel } from '../lib/chat-store.js'
@@ -277,6 +277,8 @@ export function render() {
   let showSlash = false
   let slashFilter = ''
   let gwOnline = false
+  // null = 仍在加载首次 check，先不显示 banner 防首屏闪烁
+  let hermesInstalled = null
   let currentModel = ''
   const mobileQuery = window.matchMedia('(max-width: 720px)')
 
@@ -305,11 +307,19 @@ export function render() {
   // --- initial session load + model meta ---
   store.loadSessions().then(() => draw())
   store.loadProfiles().then(() => draw()).catch(() => {})
+  // 强制刷新安装/Gateway 状态缓存，避免用户刚在仪表盘启动 Gateway 后
+  // 进聊天页看到 30s 过期的「未启动」误判。
+  invalidate('check_hermes')
   api.checkHermes().then(info => {
+    hermesInstalled = !!info?.installed
     gwOnline = !!info?.gatewayRunning
     currentModel = info?.model || ''
     draw()
-  }).catch(() => {})
+  }).catch(() => {
+    hermesInstalled = false
+    gwOnline = false
+    draw()
+  })
 
   // ----------------------------------------------------------- subscription
 
@@ -676,8 +686,8 @@ export function render() {
                    ${ICONS.stop}
                  </button>`
               : `<button class="hm-chat-send-btn" id="hm-chat-send"
-                         ${!active || !inputValue.trim() ? 'disabled' : ''}
-                         title="${escHtml(t('engine.chatSend'))}">
+                         ${(!active || !inputValue.trim() || hermesInstalled === false || !gwOnline) ? 'disabled' : ''}
+                         title="${escHtml(hermesInstalled === false ? t('engine.chatHealthInstallMissing') : !gwOnline ? t('engine.chatHealthGatewayDown') : t('engine.chatSend'))}">
                    ${ICONS.send}
                  </button>`}
           </div>
@@ -732,6 +742,31 @@ export function render() {
     `
   }
 
+  // 健康状态 banner：未装/未启动 → 在输入区上方显示一条警告 + 「去仪表盘」按钮。
+  // 首次 fetch 完成前返回空字符串，避免首屏闪烁。
+  function renderHealthBanner() {
+    if (hermesInstalled === null) return ''
+    if (hermesInstalled === false) {
+      return `
+        <div class="hm-chat-health-banner is-error">
+          <span class="hm-chat-health-icon" aria-hidden="true">⚠</span>
+          <span class="hm-chat-health-msg">${escHtml(t('engine.chatHealthInstallMissing'))}</span>
+          <a class="hm-chat-health-action" href="#/h/dashboard">${escHtml(t('engine.chatHealthGoDashboard'))}</a>
+        </div>
+      `
+    }
+    if (!gwOnline) {
+      return `
+        <div class="hm-chat-health-banner is-warn">
+          <span class="hm-chat-health-icon" aria-hidden="true">⚠</span>
+          <span class="hm-chat-health-msg">${escHtml(t('engine.chatHealthGatewayDown'))}</span>
+          <a class="hm-chat-health-action" href="#/h/dashboard">${escHtml(t('engine.chatHealthGoDashboard'))}</a>
+        </div>
+      `
+    }
+    return ''
+  }
+
   // ----------------------------------------------------------- draw
 
   function draw() {
@@ -750,6 +785,7 @@ export function render() {
         ${renderSidebar()}
         <section class="hm-chat-main">
           ${renderHeader()}
+          ${renderHealthBanner()}
           <div class="hm-chat-messages" id="hm-chat-messages">
             ${renderMessages()}
           </div>

src/engines/hermes/style/hermes.css

@@ -4577,6 +4577,50 @@ body[data-active-engine="hermes"][data-theme="dark"] {
   margin-left: 2px;
 }
 
+/* ---- Health banner (install / gateway readiness) ---- */
+[data-engine="hermes"] .hm-chat-health-banner {
+  display: flex;
+  align-items: center;
+  gap: 12px;
+  padding: 10px 28px;
+  font-size: 13px;
+  border-bottom: 1px solid var(--hm-border);
+  flex-shrink: 0;
+}
+[data-engine="hermes"] .hm-chat-health-banner.is-error {
+  background: var(--hm-error-soft);
+  color: var(--hm-error);
+}
+[data-engine="hermes"] .hm-chat-health-banner.is-warn {
+  background: var(--hm-warn-soft);
+  color: var(--hm-warn);
+}
+[data-engine="hermes"] .hm-chat-health-icon {
+  font-size: 14px;
+  line-height: 1;
+  flex-shrink: 0;
+}
+[data-engine="hermes"] .hm-chat-health-msg {
+  flex: 1;
+  line-height: 1.5;
+}
+[data-engine="hermes"] .hm-chat-health-action {
+  flex-shrink: 0;
+  padding: 4px 12px;
+  border-radius: 999px;
+  color: inherit;
+  text-decoration: none;
+  font-weight: 500;
+  font-size: 12px;
+  border: 1px solid currentColor;
+  background: transparent;
+  transition: background 0.16s ease, color 0.16s ease;
+}
+[data-engine="hermes"] .hm-chat-health-action:hover {
+  background: currentColor;
+  color: var(--hm-surface-0);
+}
+
 /* ---- Messages area ---- */
 [data-engine="hermes"] .hm-chat-messages {
   flex: 1;

src/locales/modules/engine.js

@@ -293,6 +293,18 @@ export default {
   // Short labels for the header pill — full sentence lives in the tooltip
   chatGatewayOfflineShort: _('离线', 'Offline', '離線'),
   chatGatewayOnlineShort: _('在线', 'Online', '線上'),
+  // 健康检查 banner（聊天页顶部）
+  chatHealthInstallMissing: _(
+    '未检测到 Hermes Agent 安装。请在仪表盘完成安装后再开始对话。',
+    'Hermes Agent is not installed. Please complete installation on the dashboard before chatting.',
+    '未偵測到 Hermes Agent 安裝。請在儀表板完成安裝後再開始對話。'
+  ),
+  chatHealthGatewayDown: _(
+    'Hermes Gateway 未启动，无法发送消息。请在仪表盘启动 Gateway。',
+    'Hermes Gateway is not running, messages cannot be sent. Please start the Gateway on the dashboard.',
+    'Hermes Gateway 未啟動，無法發送訊息。請在儀表板啟動 Gateway。'
+  ),
+  chatHealthGoDashboard: _('去仪表盘', 'Open Dashboard', '去儀表板'),
   chatWelcome: _('你好！我是 Hermes Agent，有什么可以帮你的？', 'Hello! I\'m Hermes Agent, how can I help?', '你好！我是 Hermes Agent，有什麼可以幫你的？'),
   chatEmptyHint: _('开始一段对话吧', 'Start a conversation', '開始一段對話吧'),
   chatEmptyTitle: _('和 Hermes Agent 对话', 'Talk to Hermes Agent', '和 Hermes Agent 對話'),