feat(hermes): Batch 1 §E - Sessions 导出（走 dashboard /api/sessions/{id}/messages）

校对稿订正：不走 CLI `hermes sessions export`，直接调 dashboard 9119 HTTP API。

## 后端
- 新 Tauri 命令 hermes_session_export(session_id):
  · GET http://127.0.0.1:{dashboard_port}/api/sessions/{id}/messages
  · 拿原始 JSON 返回前端
  · 错误提示「请先启动 Dashboard」（dashboard server 必须运行）

## 前端
- tauri-api.js: hermesSessionExport wrapper
- sessions.js: 详情面板「打开会话 / Pin / 导出 / 删除」并列布局
  · 点导出 → Blob + URL.createObjectURL + a.download 浏览器下载 hermes-session-{id}.json
  · toast 成功/失败
- dev-api.js: Web 模式 handler 同步调 dashboard 端口

## i18n
- sessionsExport / sessionsExportSuccess / sessionsExportFailed × 3 语言

src/engines/hermes/pages/sessions.js

@@ -249,6 +249,7 @@ export function render() {
           <div class="hm-session-detail-actions">
             <button class="hm-sessions-btn" id="hm-session-open-chat">${icon('message-circle', 14)}${escHtml(t('engine.sessionsOpenChat'))}</button>
             ${canPin ? `<button class="hm-sessions-btn" id="hm-session-pin">${icon(store.state.pinned.has(session.id) ? 'crown' : 'target', 14)}${escHtml(store.state.pinned.has(session.id) ? t('engine.sessionsUnpin') : t('engine.sessionsPin'))}</button>` : ''}
+            <button class="hm-sessions-btn" id="hm-session-export" data-session-id="${escAttr(session.id)}">${icon('download', 14)}${escHtml(t('engine.sessionsExport'))}</button>
             <button class="hm-sessions-btn is-danger" id="hm-session-delete" data-session-key="${escAttr(key)}">${icon('trash', 14)}${escHtml(t('engine.chatDeleteSession'))}</button>
           </div>
         </div>
@@ -454,6 +455,31 @@ export function render() {
     el.querySelector('#hm-session-delete')?.addEventListener('click', async () => {
       await deleteOne(currentSession())
     })
+
+    // Batch 1 §E: 会话导出
+    el.querySelector('#hm-session-export')?.addEventListener('click', async (e) => {
+      const sid = e.currentTarget.dataset.sessionId
+      if (!sid) return
+      const btn = e.currentTarget
+      btn.disabled = true
+      try {
+        const data = await api.hermesSessionExport(sid)
+        const blob = new Blob([JSON.stringify(data, null, 2)], { type: 'application/json' })
+        const url = URL.createObjectURL(blob)
+        const a = document.createElement('a')
+        a.href = url
+        a.download = `hermes-session-${sid}.json`
+        document.body.appendChild(a)
+        a.click()
+        a.remove()
+        URL.revokeObjectURL(url)
+        toast(t('engine.sessionsExportSuccess'), 'success')
+      } catch (err) {
+        toast(t('engine.sessionsExportFailed') + ': ' + (err?.message || err), 'error')
+      } finally {
+        btn.disabled = false
+      }
+    })
   }
 
   async function init() {

src/lib/tauri-api.js

@@ -478,6 +478,8 @@ export const api = {
   // Batch 1 §D + §C-bis: 真正中断 + Approval Flow（用 run_id）
   hermesRunStop: (runId) => invoke('hermes_run_stop', { runId }),
   hermesRunApproval: (runId, choice) => invoke('hermes_run_approval', { runId, choice }),
+  // Batch 1 §E: 会话消息导出（走 dashboard /api/sessions/{id}/messages）
+  hermesSessionExport: (sessionId) => invoke('hermes_session_export', { sessionId }),
   hermesReadConfig: () => invoke('hermes_read_config'),
   hermesReadConfigFull: () => invoke('hermes_read_config_full'),
   hermesLazyDepsFeatures: () => cachedInvoke('hermes_lazy_deps_features', {}, 600000),

src/locales/modules/engine.js

@@ -437,6 +437,10 @@ export default {
   hermesConfigStatusSaving: _('保存中…', 'Saving…', '儲存中…'),
   hermesConfigStatusLoading: _('加载中…', 'Loading…', '載入中…'),
   hermesConfigStatusReady: _('raw yaml 编辑器', 'raw yaml editor', 'raw yaml 編輯器'),
+  // Batch 1 §E: 会话导出
+  sessionsExport: _('导出', 'Export', '匯出'),
+  sessionsExportSuccess: _('已导出', 'Exported', '已匯出'),
+  sessionsExportFailed: _('导出失败', 'Export failed', '匯出失敗'),
   // 停止流式
   chatStop: _('停止', 'Stop', '停止'),
   chatStopped: _('已停止当前回复', 'Run stopped', '已停止目前回覆'),