use modifier dim instead of gray and .dim (#2273)

gray color doesn't work very well with white terminals. `.dim` doesn't
have an effect for some reason.

after:
<img width="1080" height="149" alt="image"
src="https://github.com/user-attachments/assets/26c0f8bb-550d-4d71-bd06-11b3189bc1d7"
/>

Before
<img width="1077" height="186" alt="image"
src="https://github.com/user-attachments/assets/b1fba0c7-bc4d-4da1-9754-6c0a105e8cd1"
/>

codex-rs/tui/src/bottom_pane/chat_composer.rs

@@ -731,15 +731,15 @@ impl WidgetRef for &ChatComposer {
                     .render_ref(bottom_line_rect, buf);
             }
         }
+        let border_style = if self.has_focus {
+            Style::default().fg(Color::Cyan)
+        } else {
+            Style::default().add_modifier(Modifier::DIM)
+        };
         Block::default()
-            .border_style(Style::default().dim())
             .borders(Borders::LEFT)
             .border_type(BorderType::QuadrantOutside)
-            .border_style(Style::default().fg(if self.has_focus {
-                Color::Cyan
-            } else {
-                Color::Gray
-            }))
+            .border_style(border_style)
             .render_ref(
                 Rect::new(textarea_rect.x, textarea_rect.y, 1, textarea_rect.height),
                 buf,

codex-rs/tui/src/bottom_pane/selection_popup_common.rs

@@ -93,9 +93,7 @@ pub(crate) fn render_rows(
                 spans.push(Span::raw("  "));
                 spans.push(Span::styled(
                     desc.clone(),
-                    Style::default()
-                        .fg(Color::DarkGray)
-                        .add_modifier(Modifier::DIM),
+                    Style::default().add_modifier(Modifier::DIM),
                 ));
             }
 
@@ -118,7 +116,7 @@ pub(crate) fn render_rows(
             Block::default()
                 .borders(Borders::LEFT)
                 .border_type(BorderType::QuadrantOutside)
-                .border_style(Style::default().fg(Color::DarkGray)),
+                .border_style(Style::default().add_modifier(Modifier::DIM)),
         )
         .widths([Constraint::Percentage(100)]);