fix: remove redundant preview header from editor PreviewPanel

editor/components/PreviewPanel.vue

@@ -31,7 +31,6 @@ function togglePlay() {
 
 <template>
   <div class="preview-panel">
-    <div class="preview-header">预览</div>
     <div class="preview-video" v-if="videoUrl">
       <video ref="videoRef" preload="auto" />
       <div class="preview-controls">
@@ -56,17 +55,6 @@ function togglePlay() {
   justify-content: center;
 }
 
-.preview-header {
-  padding: 14px 16px;
-  font-size: 14px;
-  color: #888;
-  border-bottom: 1px solid rgba(255,255,255,0.06);
-  text-transform: uppercase;
-  letter-spacing: 1px;
-  width: 100%;
-  flex-shrink: 0;
-}
-
 .preview-video {
   display: flex;
   flex-direction: column;