fix: rebalance system update toolbar layout

frontend/src/pages/governance/SystemUpdatePage.vue

@@ -2,14 +2,18 @@
   <div class="system-update-page">
     <h1 class="page-title-sr-only">系统更新</h1>
 
-    <header class="page-header page-header--actions-only" aria-label="页面操作">
-      <t-button variant="outline" :loading="statusLoading || historyLoading" @click="refreshPage">
-        <template #icon><t-icon name="refresh" /></template>
-        刷新状态
-      </t-button>
-    </header>
-
     <section class="update-panel" aria-label="系统版本与更新操作">
+      <header class="update-toolbar" aria-label="系统更新工具栏">
+        <div class="update-toolbar__copy">
+          <h2>系统更新</h2>
+          <p>获取版本、下载校验并安全重启应用</p>
+        </div>
+        <t-button variant="outline" :loading="statusLoading || historyLoading" @click="refreshPage">
+          <template #icon><t-icon name="refresh" /></template>
+          刷新状态
+        </t-button>
+      </header>
+
       <div class="update-heading">
         <div class="version-grid">
           <div class="version-item">
@@ -782,7 +786,7 @@ onBeforeUnmount(() => {
   min-width: 0;
 }
 
-.page-header,
+.update-toolbar,
 .update-heading,
 .update-actions,
 .section-heading,
@@ -791,10 +795,6 @@ onBeforeUnmount(() => {
   align-items: center;
 }
 
-.page-header {
-  justify-content: flex-end;
-}
-
 .update-panel,
 .history-panel {
   width: 100%;
@@ -818,6 +818,31 @@ onBeforeUnmount(() => {
   min-width: 0;
 }
 
+.update-toolbar {
+  justify-content: space-between;
+  gap: 20px;
+  min-width: 0;
+  padding-bottom: 2px;
+}
+
+.update-toolbar__copy {
+  min-width: 0;
+}
+
+.update-toolbar__copy h2 {
+  margin: 0;
+  color: var(--td-text-color-primary);
+  font-size: 18px;
+  line-height: 26px;
+}
+
+.update-toolbar__copy p {
+  margin: 4px 0 0;
+  color: var(--td-text-color-secondary);
+  font-size: 13px;
+  line-height: 20px;
+}
+
 .version-grid {
   display: grid;
   grid-template-columns: repeat(3, minmax(150px, 1fr));
@@ -1022,6 +1047,16 @@ onBeforeUnmount(() => {
     gap: 12px;
   }
 
+  .update-toolbar {
+    align-items: flex-start;
+    flex-direction: column;
+    gap: 10px;
+  }
+
+  .update-toolbar :deep(.t-button) {
+    width: 100%;
+  }
+
   .update-actions,
   .update-actions :deep(.t-button) {
     width: 100%;