show only an in-flight ring on the library surfaces

A finished download no longer draws anything on album covers, artist rows or
playlist rows: the badge is the progress ring alone, so a fully downloaded tile
looks like any other. The ring takes the theme's primary for the arc over a
theme track, with the one soft shadow, instead of the white glyph and its
outline.

app/src/test/kotlin/com/subtracks/ui/components/DownloadIndicatorTest.kt

@@ -11,7 +11,7 @@ class DownloadIndicatorTest {
     }
 
     @Test
-    fun aListWithNothingStartedButNoSongsShowsNothing() {
+    fun aPopulatedButUnstartedListShowsNothing() {
         assertEquals(DownloadIndicator.Hidden, ListDownloadStatus(total = 4).indicator())
     }
 
@@ -31,7 +31,7 @@ class DownloadIndicatorTest {
     }
 
     @Test
-    fun aFullyDownloadedListShowsDone() {
-        assertEquals(DownloadIndicator.Complete, ListDownloadStatus(total = 4, downloaded = 4).indicator())
+    fun aFullyDownloadedListShowsNothing() {
+        assertEquals(DownloadIndicator.Hidden, ListDownloadStatus(total = 4, downloaded = 4).indicator())
     }
 }