播放器UI优化: 上移顶部、缩小胶囊、修复进度条抖动

- 顶部padding从LumaSpacing.md(16dp)减到LumaSpacing.xs(8dp)
- 胶囊框padding从16dp/2dp减到12dp/0dp，字体12sp→11sp
- 进度条抖动修复：seek完成后延迟300ms重置isSeeking
  防止轮询循环在player追上之前覆盖currentPositionMs
- 新增seekCompletedVersion计数器触发延迟重置

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

app/src/main/kotlin/com/example/myapplication/screens/VideoPlayerScreen.kt

@@ -904,7 +904,7 @@ fun VideoPlayerScreen(
                         }
                     }
 
-                    Column(Modifier.fillMaxWidth().statusBarsPadding().padding(top = LumaSpacing.md)) {
+                    Column(Modifier.fillMaxWidth().statusBarsPadding().padding(top = LumaSpacing.xs)) {
                         // 第一排：时间（左）| 网速+电量（右）
                         Row(
                             Modifier.fillMaxWidth().padding(horizontal = capsuleInset),
@@ -1030,7 +1030,7 @@ fun VideoPlayerScreen(
                                         borderColor = Color.White.copy(alpha = 0.22f),
                                         shadowElevation = 4.dp,
                                     )
-                                    .padding(horizontal = 16.dp, vertical = 2.dp),
+                                    .padding(horizontal = 12.dp, vertical = 0.dp),
                             ) {
                                 var totalDurationMs by remember(player) {
                                     mutableLongStateOf(player.duration.coerceAtLeast(0L))
@@ -1041,6 +1041,15 @@ fun VideoPlayerScreen(
                                 var isSeeking by remember { mutableStateOf(false) }
                                 var seekPosition by remember { mutableFloatStateOf(0f) }
                                 var bufferProgress by remember { mutableFloatStateOf(0f) }
+                                var seekCompletedVersion by remember { mutableIntStateOf(0) }
+
+                                // Reset isSeeking after seek completes to prevent jitter
+                                LaunchedEffect(seekCompletedVersion) {
+                                    if (seekCompletedVersion > 0) {
+                                        delay(300)
+                                        isSeeking = false
+                                    }
+                                }
 
                                 LaunchedEffect(player) {
                                     while (true) {
@@ -1056,9 +1065,9 @@ fun VideoPlayerScreen(
                                     }
                                 }
 
-                                Row(verticalAlignment = Alignment.CenterVertically) {
+                                Row(verticalAlignment = Alignment.CenterVertically, modifier = Modifier.padding(vertical = 2.dp)) {
                                     val swipePositionMs = seekPreviewPositionMs
-                                    Text(formatMs(swipePositionMs ?: currentPositionMs), color = Color.White, fontSize = 12.sp)
+                                    Text(formatMs(swipePositionMs ?: currentPositionMs), color = Color.White, fontSize = 11.sp)
                                     LumaSeekBar(
                                         value = when {
                                             isSeeking -> seekPosition
@@ -1076,10 +1085,13 @@ fun VideoPlayerScreen(
                                             player.seekTo(targetPosition)
                                             progress = finalValue
                                             currentPositionMs = targetPosition
-                                            isSeeking = false
                                             controlsInteractionLocked = false
                                             latestOnPlaybackProgress(targetPosition, !player.isPlaying, "TimeUpdate", true)
+                                            // Keep isSeeking true briefly to prevent polling loop from
+                                            // overwriting currentPositionMs before player catches up
+                                            seekCompletedVersion++
                                         },
+                                        modifier = Modifier.weight(1f).padding(horizontal = 12.dp),
                                         progressContentDescription = stringResource(Res.string.player_progress),
                                         modifier = Modifier.weight(1f).padding(horizontal = 12.dp),
                                         activeColor = Color.White,
@@ -1088,7 +1100,7 @@ fun VideoPlayerScreen(
                                         bufferedValue = bufferProgress,
                                         thumbColor = Color.White,
                                     )
-                                    Text(formatMs(totalDurationMs), color = Color.White, fontSize = 12.sp)
+                                    Text(formatMs(totalDurationMs), color = Color.White, fontSize = 11.sp)
                                 }
                             }
                         }