feat: 播放控制移入页眉 + 媒体铺满智能裁切

页眉播放控制（仅媒体轮播页）：
- 新增 MediaHeaderControls：播放/暂停、上一段/下一段、序号、当前文件名（点击进后台）、声音解锁
- 新增 mediaControl 共享状态桥：媒体页同步播放状态，页眉订阅渲染并下发指令
- 移除媒体页底部控制区，媒体区保持纯净全屏

媒体展示：
- .ms-media 改为 object-fit: cover，填满整个容器并智能居中裁切（原 contain 留黑边）

修复：
- MediaScreen useEffect 依赖数组引用后声明函数导致的 TDZ 崩溃
- 清理 MediaScreen 中不再使用的 Icon/cleanName/togglePlayPause

src/styles/mediascreen.css

@@ -67,13 +67,14 @@
   -webkit-backdrop-filter: blur(14px);
 }
 
-/* 媒体播放器（铺满媒体区，等比适配） */
+/* 媒体播放器（填满整个媒体区，等比裁切铺满） */
 .ms-media {
   position: absolute;
   inset: 0;
   width: 100%;
   height: 100%;
-  object-fit: contain;
+  object-fit: cover;
+  object-position: center;
   background: transparent;
 }
 
@@ -109,127 +110,7 @@
   border-bottom: 1px solid rgba(47, 107, 255, 0.3);
 }
 
-/* 右下角轻量播放控制（弱化悬浮） */
-.ms-controls {
-  position: absolute;
-  right: 16px;
-  bottom: 14px;
-  left: auto;
-  transform: none;
-  z-index: 10;
-  display: flex;
-  align-items: center;
-  gap: 8px;
-  padding: 6px 12px;
-  background: rgba(255, 255, 255, 0.55);
-  border: 1px solid rgba(120, 160, 220, 0.16);
-  border-radius: 30px;
-  backdrop-filter: blur(12px);
-  -webkit-backdrop-filter: blur(12px);
-  box-shadow: 0 6px 22px rgba(56, 100, 170, 0.12);
-  opacity: 0;
-  transition: opacity 0.5s ease;
-}
-.ms-controls.visible { opacity: 1; }
-
-.ms-play {
-  width: 30px;
-  height: 30px;
-  border-radius: 50%;
-  border: none;
-  display: flex;
-  align-items: center;
-  justify-content: center;
-  color: #fff;
-  background: linear-gradient(140deg, var(--bd-blue, #2f6bff), var(--bd-cyan, #4cc2ff));
-  cursor: pointer;
-  box-shadow: 0 4px 12px rgba(47, 107, 255, 0.3);
-  transition: transform 0.2s;
-}
-.ms-play:hover { transform: scale(1.08); }
-
-.ms-nav {
-  display: flex;
-  align-items: center;
-  gap: 6px;
-}
-.ms-nav button {
-  width: 26px;
-  height: 26px;
-  border-radius: 50%;
-  border: 1px solid rgba(47, 107, 255, 0.18);
-  background: rgba(255, 255, 255, 0.6);
-  color: var(--bd-blue, #2f6bff);
-  display: flex;
-  align-items: center;
-  justify-content: center;
-  cursor: pointer;
-  transition: all 0.2s;
-}
-.ms-nav button:hover {
-  background: rgba(47, 107, 255, 0.12);
-  border-color: rgba(47, 107, 255, 0.5);
-}
-.ms-nav-num {
-  display: inline-flex;
-  align-items: baseline;
-  gap: 3px;
-  font-family: "JetBrains Mono", "Oswald", monospace;
-}
-.ms-nav-num b {
-  font-size: 13px;
-  color: var(--bd-ink, #1d2c44);
-}
-.ms-nav-num em {
-  font-style: normal;
-  font-size: 10.5px;
-  color: var(--bd-sub, #7d8fa9);
-}
-
-.ms-now {
-  display: flex;
-  align-items: center;
-  gap: 6px;
-  padding-left: 10px;
-  border-left: 1px solid rgba(47, 107, 255, 0.12);
-}
-.ms-now-dot {
-  width: 6px;
-  height: 6px;
-  border-radius: 50%;
-  background: var(--bd-green, #17b26a);
-  box-shadow: 0 0 8px rgba(23, 178, 106, 0.8);
-  animation: msPulse 1.6s ease-in-out infinite;
-}
-@keyframes msPulse {
-  0%, 100% { opacity: 1; transform: scale(1); }
-  50% { opacity: 0.4; transform: scale(0.75); }
-}
-.ms-now-name {
-  font-size: 11px;
-  font-weight: 500;
-  color: var(--bd-sub, #7d8fa9);
-  max-width: 160px;
-  overflow: hidden;
-  text-overflow: ellipsis;
-  white-space: nowrap;
-}
-
-/* 声音提示 */
-.ms-sound {
-  display: inline-flex;
-  align-items: center;
-  gap: 6px;
-  padding: 5px 11px;
-  font-size: 11px;
-  font-weight: 500;
-  color: #4a5b76;
-  background: rgba(255, 255, 255, 0.75);
-  border: 1px solid rgba(47, 107, 255, 0.14);
-  border-radius: 30px;
-  cursor: pointer;
-}
-.ms-sound .appica-ico { color: var(--bd-blue, #2f6bff); }
+/* 播放控制已上移页眉（见 datascreen.css .bd-hd-media） */
 
 /* 页脚 */
 .ms-page .bd-strip { z-index: 10; position: relative; }