refactor(ui): improve TileBar rendering and width calculation

Update TileBar to use UnicodeWidthStr for accurate text width calculation and
improve axis display.

- Use `unicode_width::UnicodeWidthStr` for calculating label and hint widths
- Move `axis_display` to a static method on `TileBar`
- Update axis symbols for better visual clarity (e.g., '|', '-', '=', '.')
- Clear the tile bar area before rendering to prevent stale characters

Co-Authored-By: fiddlerwoaroof/git-smart-commit (unsloth/gemma-4-26B-A4B-it-GGUF:UD-Q5_K_XL)

src/ui/tile_bar.rs

@@ -32,10 +32,26 @@ impl<'a> TileBar<'a> {
             tile_cat_idx,
         }
     }
+    fn axis_display(axis: Axis) -> (&'static str, Color) {
+        match axis {
+            Axis::Row => ("|", Color::Green),
+            Axis::Column => ("-", Color::Blue),
+            Axis::Page => ("=", Color::Magenta),
+            Axis::None => (".", Color::DarkGray),
+        }
+    }
 }
 
 impl<'a> Widget for TileBar<'a> {
     fn render(self, area: Rect, buf: &mut Buffer) {
+        // Clear the line to avoid stale characters from previous renders
+        buf.set_string(
+            area.x,
+            area.y,
+            " ".repeat(area.width as usize),
+            Style::default(),
+        );
+
         let view = self.model.active_view();
 
         let selected_cat_idx = if matches!(self.mode, AppMode::TileSelect) {
@@ -50,7 +66,7 @@ impl<'a> Widget for TileBar<'a> {
 
         let cat_names: Vec<&str> = self.model.category_names();
         for (i, cat_name) in cat_names.iter().enumerate() {
-            let (axis_symbol, axis_color) = axis_display(view.axis_of(cat_name));
+            let (axis_symbol, axis_color) = TileBar::axis_display(view.axis_of(cat_name));
             let label = format!(" [{cat_name} {axis_symbol}] ");
             let is_selected = selected_cat_idx == Some(i);
 
@@ -63,22 +79,23 @@ impl<'a> Widget for TileBar<'a> {
                 Style::default().fg(axis_color)
             };
 
-            if x + label.len() as u16 > area.x + area.width {
+            let label_w = label.width() as u16;
+            if x + label_w > area.x + area.width {
                 break;
             }
             buf.set_string(x, area.y, &label, style);
-            x += label.len() as u16;
+            x += label_w;
         }
 
         // Hint
         if matches!(self.mode, AppMode::TileSelect) {
             let hint = " [Enter] cycle axis  [r/c/p] set axis  [←→] select  [Esc] cancel";
-            if x + hint.len() as u16 <= area.x + area.width {
+            if x + hint.width() as u16 <= area.x + area.width {
                 buf.set_string(x, area.y, hint, Style::default().fg(Color::DarkGray));
             }
         } else {
             let hint = " Ctrl+↑↓←→ to move tiles";
-            if x + hint.len() as u16 <= area.x + area.width {
+            if x + hint.width() as u16 <= area.x + area.width {
                 buf.set_string(x, area.y, hint, Style::default().fg(Color::DarkGray));
             }
         }