W10: Active panel focus indicator bar

Add a bright accent-coloured 1-column bar on the inner left edge
of the active panel. This is a premium TUI pattern (also used by
bottom, lazygit, btop) that gives a much clearer visual focus
indicator than a border colour change alone.

The bar uses the same active_border_color as the panel border so
it stays thematically consistent. The panel inner content shifts
right by one column to accommodate the bar without losing content.

Tests: 1388 pass, zero warnings.

local/recipes/tui/tlc/source/src/filemanager/render.rs

@@ -320,6 +320,21 @@ impl FileManager {
             return;
         }
 
+        if active && inner.width >= 3 {
+            let bar = Paragraph::new(Span::styled(
+                " ",
+                Style::default().bg(active_border_color),
+            ));
+            let mut bar_area = inner;
+            bar_area.width = 1;
+            frame.render_widget(bar, bar_area);
+        }
+        let inner = if active && inner.width >= 3 {
+            Rect::new(inner.x + 1, inner.y, inner.width - 1, inner.height)
+        } else {
+            inner
+        };
+
         let show_meta = inner.height >= 3;
         let show_footer = inner.height >= 2;
         let body_y = inner.y + u16::from(show_meta);