feat(android): NowPlaying drag-down-to-dismiss + close button

Audit v2 missing UX: full player had no way to escape except system
back. Two additions:

- Chevron-down close button as the Scaffold topBar navigation icon.
  Transparent background so the gradient/cover behind shows through.
- Vertical drag-down on the whole screen pops back past a 200px
  threshold, mirroring Flutter's modal-page gesture. Horizontal
  scrubs on the slider still work because the gesture detector is
  specifically vertical-only.

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

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

@@ -17,8 +17,14 @@ import androidx.compose.foundation.shape.RoundedCornerShape
 import androidx.compose.material3.Icon
 import androidx.compose.material3.IconButton
 import androidx.compose.material3.MaterialTheme
+import androidx.compose.foundation.gestures.detectVerticalDragGestures
 import androidx.compose.material3.Scaffold
 import androidx.compose.material3.Slider
+import androidx.compose.material3.TopAppBar
+import androidx.compose.material3.TopAppBarDefaults
+import androidx.compose.material3.ExperimentalMaterial3Api
+import androidx.compose.ui.graphics.Color
+import androidx.compose.ui.input.pointer.pointerInput
 import androidx.compose.material3.SliderDefaults
 import androidx.compose.material3.SnackbarHost
 import androidx.compose.material3.SnackbarHostState
@@ -38,6 +44,7 @@ import androidx.hilt.navigation.compose.hiltViewModel
 import androidx.lifecycle.compose.collectAsStateWithLifecycle
 import androidx.navigation.NavHostController
 import coil3.compose.AsyncImage
+import com.composables.icons.lucide.ChevronDown
 import com.composables.icons.lucide.ListMusic
 import com.composables.icons.lucide.Lucide
 import com.composables.icons.lucide.Music
@@ -64,6 +71,12 @@ private const val MS_PER_SECOND = 1000L
 private const val SECONDS_PER_MINUTE = 60L
 private const val POP_GRACE_MS = 500L
 
+// Vertical drag-down threshold (in pixels) past which the gesture
+// pops the player. Matches Flutter's 80px threshold in spirit;
+// using pointer-input pixels not dp because gesture velocity also
+// participates in the dismiss decision.
+private const val DRAG_DISMISS_THRESHOLD_PX = 200f
+
 /**
  * Full-screen player. Shows the cover (placeholder until AlbumRef join
  * lands), title + artist + album, a scrubber, and a transport row
@@ -99,7 +112,8 @@ fun NowPlayingScreen(
         return
     }
     Scaffold(
-        modifier = Modifier.fillMaxSize(),
+        modifier = Modifier.fillMaxSize().nowPlayingDragDismiss(navController),
+        topBar = { NowPlayingTopBar(onClose = { navController.popBackStack() }) },
         snackbarHost = { SnackbarHost(snackbarHostState) },
         containerColor = MaterialTheme.colorScheme.background,
     ) { inner ->
@@ -113,6 +127,50 @@ fun NowPlayingScreen(
     }
 }
 
+/**
+ * Drag-down to dismiss. Mirrors Flutter's modal-page gesture: a
+ * downward drag past the threshold pops the screen, returning the
+ * user to whichever shell route launched NowPlaying. Tap, swipe-up,
+ * and horizontal drags pass through to the underlying content
+ * (slider scrub, etc.).
+ */
+@Composable
+private fun Modifier.nowPlayingDragDismiss(navController: NavHostController): Modifier =
+    this.pointerInput(Unit) {
+        var totalDragY = 0f
+        detectVerticalDragGestures(
+            onDragStart = { totalDragY = 0f },
+            onDragEnd = {
+                if (totalDragY > DRAG_DISMISS_THRESHOLD_PX) {
+                    navController.popBackStack()
+                }
+                totalDragY = 0f
+            },
+            onDragCancel = { totalDragY = 0f },
+            onVerticalDrag = { _, delta -> totalDragY += delta },
+        )
+    }
+
+@OptIn(ExperimentalMaterial3Api::class)
+@Composable
+private fun NowPlayingTopBar(onClose: () -> Unit) {
+    TopAppBar(
+        title = {},
+        navigationIcon = {
+            IconButton(onClick = onClose) {
+                Icon(
+                    imageVector = Lucide.ChevronDown,
+                    contentDescription = "Close player",
+                    tint = MaterialTheme.colorScheme.onSurface,
+                )
+            }
+        },
+        colors = TopAppBarDefaults.topAppBarColors(
+            containerColor = Color.Transparent,
+        ),
+    )
+}
+
 @Composable
 private fun NowPlayingBody(
     inner: androidx.compose.foundation.layout.PaddingValues,