v0.31.6: album art inside the playlists' frame; text and playhead lifted 2px

The playlist list and the album art under it share one frame (the list's
own style, drawn around both), and the no-art placeholder is a shade
lighter than that frame line so the line still reads around it. The
playlist name, times and playhead sit 2px up (HeaderRow.LIFT), on the
Library button's bottom line by eye.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tests/test_round69.py

@@ -52,6 +52,8 @@ def test_library_button_spans_the_playlist_list(qapp, tmp_path):
     window = _window(qapp, tmp_path)
     header = window.sidebar.header
     lists = window.sidebar.list_area
+    # The frame around the playlists takes in the album art too.
+    assert window.sidebar.art.parentWidget() is lists
     assert header.parentWidget() is not window.sidebar
     assert _gx(header) == _gx(lists) > _gx(window)
     assert header.width() == lists.width()
@@ -71,12 +73,13 @@ def test_header_row_items_share_one_floor(qapp, tmp_path):
 
     assert bottom(window.sidebar.library_button) == floor
     assert bottom(window._library_view._search) == floor
-    assert bottom(window._transport._slider) == floor
+    # Text and the playhead sit LIFT px up, on the button's bottom line by eye.
+    assert bottom(window._transport._slider) == floor - HeaderRow.LIFT
     window._show_playlist("abcd1234")
     qapp.processEvents()
     label = window._playlist_view.header
     baseline = bottom(label) - label.fontMetrics().descent()
-    assert abs(baseline - floor) <= 1
+    assert abs(baseline - (floor - HeaderRow.LIFT)) <= 1
 
 
 def test_search_then_title_sit_where_the_view_starts(qapp, tmp_path):