fix(android): NowPlaying drag-down dismiss via NestedScroll (#2)

The previous detectVerticalDragGestures modifier on the Scaffold
never fired because the body Column applies verticalScroll, which
wins the touch-slop competition for every vertical drag delta
before the outer detector sees it. User-visible symptom: swiping
down on the NowPlaying screen did nothing.

Replace with a NestedScrollConnection. verticalScroll offers its
over-scroll deltas to the nearest ancestor connection via the
standard nested-scroll protocol; when the column is at the top of
its scroll range, downward drag deltas surface in onPostScroll
unconsumed (available.y > 0). Accumulate those toward a 200 px
threshold and pop the back stack.

- Upward over-scroll or any consumed delta resets the accumulator
  so a partial drag-down followed by drag-up doesn't latch.
- onPreFling resets on lift-off so a lazy swipe doesn't dismiss
  later after the user has released.
- Slider thumb retains its own pointerInput and is not affected.
- Source filter (UserInput) ignores nested-scroll-driven
  animations (e.g. flings from inner scrollables).

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

@@ -22,7 +22,11 @@ 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.ui.geometry.Offset
+import androidx.compose.ui.input.nestedscroll.NestedScrollConnection
+import androidx.compose.ui.input.nestedscroll.NestedScrollSource
+import androidx.compose.ui.input.nestedscroll.nestedScroll
+import androidx.compose.ui.unit.Velocity
 import androidx.compose.material3.Scaffold
 import androidx.compose.material3.Slider
 import androidx.compose.material3.TopAppBar
@@ -30,7 +34,6 @@ import androidx.compose.material3.TopAppBarDefaults
 import androidx.compose.material3.ExperimentalMaterial3Api
 import androidx.compose.ui.graphics.Brush
 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
@@ -122,8 +125,11 @@ fun NowPlayingScreen(
         return
     }
     val dominant = rememberDominantColor(track.coverUrl)
+    val dismissConnection = rememberDragDismissConnection(
+        onDismiss = { navController.popBackStack() },
+    )
     Scaffold(
-        modifier = Modifier.fillMaxSize().nowPlayingDragDismiss(navController),
+        modifier = Modifier.fillMaxSize().nestedScroll(dismissConnection),
         topBar = { NowPlayingTopBar(onClose = { navController.popBackStack() }) },
         snackbarHost = { SnackbarHost(snackbarHostState) },
         containerColor = Color.Transparent,
@@ -161,27 +167,50 @@ private const val DOMINANT_TINT_MID_STOP = 0.45f
 
 /**
  * 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.).
+ * downward over-scroll past the threshold pops the screen.
+ *
+ * Implementation note: the body Column uses verticalScroll, which
+ * eats every vertical drag delta before a top-level
+ * detectVerticalDragGestures can see it. NestedScroll is the
+ * right primitive here — verticalScroll offers its over-scroll
+ * deltas to the nearest ancestor connection, so we accumulate
+ * downward over-scroll (available.y > 0 means the scrollable
+ * couldn't consume it because it's at the top) and pop on
+ * threshold. The Slider keeps its own pointerInput and is
+ * unaffected.
  */
 @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()
+private fun rememberDragDismissConnection(
+    onDismiss: () -> Unit,
+    thresholdPx: Float = DRAG_DISMISS_THRESHOLD_PX,
+): NestedScrollConnection = remember(onDismiss, thresholdPx) {
+    object : NestedScrollConnection {
+        private var accumulated = 0f
+
+        override fun onPostScroll(
+            consumed: Offset,
+            available: Offset,
+            source: NestedScrollSource,
+        ): Offset {
+            if (source != NestedScrollSource.UserInput) return Offset.Zero
+            if (available.y > 0f) {
+                accumulated += available.y
+                if (accumulated >= thresholdPx) {
+                    accumulated = 0f
+                    onDismiss()
                 }
-                totalDragY = 0f
-            },
-            onDragCancel = { totalDragY = 0f },
-            onVerticalDrag = { _, delta -> totalDragY += delta },
-        )
+                return Offset(0f, available.y)
+            }
+            if (consumed.y != 0f || available.y < 0f) accumulated = 0f
+            return Offset.Zero
+        }
+
+        override suspend fun onPreFling(available: Velocity): Velocity {
+            accumulated = 0f
+            return Velocity.Zero
+        }
     }
+}
 
 @OptIn(ExperimentalMaterial3Api::class)
 @Composable