feat(ui): draw pane frames, page keys and a scroll thumb

beefy_player/widgets/header.py

@@ -74,6 +74,11 @@ class HeaderBar(Widget):
         lines: list[Text] = []
         for index, row in enumerate(hero):
             line = _hero_line(row, index, hero_width, gradient_fill)
+            # Art rows are right-trimmed, so a row ending in a blank cell is a
+            # column short; pad it back or the caption and clock drift left.
+            short = hero_width - cell_len(line.plain)
+            if short > 0:
+                line.append(" " * short)
             if show_middle and text_offset <= index < text_offset + len(hero_lines):
                 middle = hero_lines[index - text_offset]
                 line.append(" " * 4)