feat(android): swipe-up-to-expand gesture on MiniPlayer (#34)

Ports player_bar.dart's onVerticalDragEnd — an upward flick anywhere on
the bar expands into NowPlaying, alongside the existing tap-to-expand. A
vertical draggable claims only vertical-dominant drags, so the inline
seek slider keeps its horizontal scrub gesture. The 200 px/s Flutter
threshold is expressed in dp and density-converted so the flick feels
the same across screen densities.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

android/app/src/main/java/com/fabledsword/minstrel/player/ui/MiniPlayer.kt

@@ -4,6 +4,9 @@ import androidx.compose.animation.Crossfade
 import androidx.compose.animation.ExperimentalSharedTransitionApi
 import androidx.compose.foundation.background
 import androidx.compose.foundation.clickable
+import androidx.compose.foundation.gestures.Orientation
+import androidx.compose.foundation.gestures.draggable
+import androidx.compose.foundation.gestures.rememberDraggableState
 import androidx.compose.foundation.layout.Box
 import androidx.compose.foundation.layout.Column
 import androidx.compose.foundation.layout.Row
@@ -27,6 +30,7 @@ import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.draw.clip
 import androidx.compose.ui.layout.ContentScale
+import androidx.compose.ui.platform.LocalDensity
 import androidx.compose.ui.text.style.TextOverflow
 import androidx.compose.ui.unit.dp
 import androidx.hilt.navigation.compose.hiltViewModel
@@ -52,6 +56,11 @@ private const val MINI_BAR_TONAL_ELEVATION_DP = 4
 private const val COVER_SIZE_DP = 48
 private const val SCRUBBER_ROW_HEIGHT_DP = 4
 
+// Upward flick speed (dp/s) that expands the bar into NowPlaying.
+// Mirrors player_bar.dart's 200 px/s threshold; expressed in dp and
+// converted via density so the gesture feels the same across screens.
+private const val SWIPE_UP_VELOCITY_DP = 200
+
 @OptIn(ExperimentalSharedTransitionApi::class)
 @Composable
 private fun MiniCover(coverUrl: String, contentDescription: String) {
@@ -126,10 +135,22 @@ fun MiniPlayer(
     val isLiked by trackActionsViewModel.isLikedFlow(track.id)
         .collectAsStateWithLifecycle(initialValue = false)
 
+    // Swipe up anywhere on the bar to expand into the full player —
+    // mirrors player_bar.dart. We only act on a clear upward flick
+    // (negative velocity past the threshold) so a slow tap-with-jitter
+    // doesn't accidentally open the screen. The horizontal seek slider
+    // keeps its own gestures; a vertical draggable only claims
+    // vertical-dominant drags.
+    val flickThresholdPx = with(LocalDensity.current) { SWIPE_UP_VELOCITY_DP.dp.toPx() }
     Surface(
         modifier = modifier
             .fillMaxWidth()
-            .height(MINI_BAR_HEIGHT_DP.dp),
+            .height(MINI_BAR_HEIGHT_DP.dp)
+            .draggable(
+                orientation = Orientation.Vertical,
+                state = rememberDraggableState { },
+                onDragStopped = { velocity -> if (velocity < -flickThresholdPx) onExpandClick() },
+            ),
         color = MaterialTheme.colorScheme.surface,
         tonalElevation = MINI_BAR_TONAL_ELEVATION_DP.dp,
     ) {