align the swipe peek with the skip and harden its edges

Resolve previousItem/upcomingItem through the same offline download scan the transport uses, so the peeking art is the track the swipe will actually play. Clear a frozen strip when a fallback swipe fires, prefer the dragged direction over an opposite fling, and simplify the hand-back and ratio prefetch.

app/src/test/kotlin/com/subtracks/playback/PlaybackControllerTest.kt

@@ -230,6 +230,36 @@ class PlaybackControllerTest {
         }
     }
 
+    @Test
+    fun offlinePreviousItemMatchesTheTrackPreviousSkipsTo() {
+        seedAlbum(5, sourceId = 1)
+        markDownloaded(1, "s1")
+        markDownloaded(1, "s4")
+        setOffline()
+        controller.playAlbum(1, "al1", 3)
+        await {
+            controller.state.value.item
+                ?.id == "s4"
+        }
+
+        assertEquals("s1", runBlocking { controller.previousItem()?.id })
+    }
+
+    @Test
+    fun offlineUpcomingItemMatchesTheTrackNextPlays() {
+        seedAlbum(4, sourceId = 1)
+        markDownloaded(1, "s1")
+        markDownloaded(1, "s3")
+        setOffline()
+        controller.playAlbum(1, "al1", 0)
+        await {
+            controller.state.value.item
+                ?.id == "s1"
+        }
+
+        assertEquals("s3", runBlocking { controller.upcomingItem()?.id })
+    }
+
     @Test
     fun advancingShiftsTheWindowAndKeepsItBounded() {
         seedAlbum(100, sourceId = 1)

app/src/test/kotlin/com/subtracks/ui/playback/NowPlayingTapsTest.kt

@@ -231,6 +231,30 @@ class NowPlayingTapsTest {
         )
     }
 
+    @Test
+    fun theSwipeActionPrefersTheDraggedDirectionOverAnOppositeFling() {
+        assertEquals(
+            SwipeAction.CommitPrevious,
+            swipeAction(offsetX = 300f, velocity = -2_000f, width = 1_000f, canGoNext = true, canGoPrevious = true),
+        )
+        assertEquals(
+            SwipeAction.CommitNext,
+            swipeAction(offsetX = -300f, velocity = 2_000f, width = 1_000f, canGoNext = true, canGoPrevious = true),
+        )
+    }
+
+    @Test
+    fun swipingLeftWithANeighbourRotatesTheStrip() {
+        render(nextArt = adjacentArt("s-next"))
+
+        composeRule.onNodeWithTag(NOW_PLAYING_NEXT_TAG, useUnmergedTree = true).assertExists()
+        composeRule.onNodeWithTag(NOW_PLAYING_COVER_TAG).performTouchInput { swipeLeft() }
+        composeRule.waitForIdle()
+
+        composeRule.onNodeWithTag(NOW_PLAYING_NEXT_TAG, useUnmergedTree = true).assertDoesNotExist()
+        composeRule.onNodeWithTag(NOW_PLAYING_PREVIOUS_TAG, useUnmergedTree = true).assertExists()
+    }
+
     @Test
     fun rotatingTheStripMovesTheNeighbourIntoTheCentre() {
         val a = adjacentArt("a")