fix(ui): mark sidebar focus with an accent colour, not bold (#25)

The focused sidebar panel border (ADR-0046 DC3) was bright `fg` plus
`Modifier::BOLD`. Bold box-drawing glyphs render as broken/gapped
line-art in the asciinema cast player and are fragile in some terminals.

`panel_border_style` now marks focus with a non-bold accent colour
(`theme.mode_simple`, blue); the unfocused border stays muted. Bold is
untouched on text spans (titles, key hints) — the constraint is
specifically that box-drawing borders carry no bold attribute.

Pure style change: the Tier-2 snapshots are text-only so none needed
re-accepting; the Tier-1 assertion was updated and a render-level test
now checks the rendered border cells carry the accent and no bold.

ADR-0046 Amendment 1.

src/ui.rs

@@ -275,13 +275,15 @@ fn render_nav_sidebar_overlay(app: &mut App, theme: &Theme, frame: &mut Frame<'_
     render_relationships_panel(app, theme, frame, parts[1]);
 }
 
-/// Border style for a sidebar panel: an accented, bold border when it
-/// holds navigation focus (ADR-0046 DC3), the muted border otherwise.
+/// Border style for a sidebar panel: a non-bold **accent colour**
+/// border when it holds navigation focus (ADR-0046 DC3, refined by
+/// Amendment 1 / issue #25), the muted border otherwise. The focus
+/// cue is the accent hue, NOT `Modifier::BOLD` — bold box-drawing
+/// glyphs render as broken/gapped line-art in the asciinema player
+/// and are fragile in some terminals.
 fn panel_border_style(theme: &Theme, focused: bool) -> Style {
     if focused {
-        Style::default()
-            .fg(theme.fg)
-            .add_modifier(Modifier::BOLD)
+        Style::default().fg(theme.mode_simple)
     } else {
         Style::default().fg(theme.border)
     }
@@ -3027,16 +3029,76 @@ mod tests {
 
     #[test]
     fn focused_panel_gets_an_accent_border() {
-        // ADR-0046 DC3: the focused sidebar panel is accent-bordered.
+        // ADR-0046 DC3 (Amendment 1, issue #25): the focused sidebar
+        // panel is marked by a non-bold accent COLOUR, not bold. Bold
+        // box-drawing glyphs render as broken/gapped line-art in the
+        // asciinema player (and are fragile in some terminals), so the
+        // focus cue is the accent hue against the muted unfocused
+        // border — never a `Modifier::BOLD` on the border.
         let theme = Theme::dark();
         let focused = panel_border_style(&theme, true);
         let normal = panel_border_style(&theme, false);
-        assert_eq!(focused.fg, Some(theme.fg));
-        assert!(focused.add_modifier.contains(Modifier::BOLD));
+        assert_eq!(focused.fg, Some(theme.mode_simple));
+        assert!(
+            !focused.add_modifier.contains(Modifier::BOLD),
+            "the focused border must NOT be bold (issue #25)",
+        );
         assert_eq!(normal.fg, Some(theme.border));
         assert!(!normal.add_modifier.contains(Modifier::BOLD));
     }
 
+    #[test]
+    fn focused_panel_border_cells_are_accent_colour_not_bold() {
+        // Full-stack guard for issue #25: the accent colour (and the
+        // absence of bold) must reach the actual rendered border cells,
+        // not just `panel_border_style` in isolation. With the Tables
+        // panel focused, its box-drawing border cells carry
+        // `theme.mode_simple` and never `Modifier::BOLD`; with no panel
+        // focused, no border cell wears the accent colour.
+        const BOX_DRAWING: &[char] = &['╭', '╮', '╰', '╯', '─', '│'];
+        let is_border = |sym: &str| sym.chars().all(|c| BOX_DRAWING.contains(&c));
+        let theme = Theme::dark();
+
+        let mut app = App::new();
+        app.tables = vec!["Customers".to_string(), "Orders".to_string()];
+        app.nav_focus = NavFocus::SidebarTables;
+        let buf = render_to_buffer(&mut app, &theme, 110, 24);
+        let mut accent_border_cells = 0;
+        for y in 0..buf.area.height {
+            for x in 0..buf.area.width {
+                let cell = &buf[(x, y)];
+                if is_border(cell.symbol()) && cell.fg == theme.mode_simple {
+                    accent_border_cells += 1;
+                    assert!(
+                        !cell.modifier.contains(Modifier::BOLD),
+                        "focused border cell at ({x},{y}) must not be bold (issue #25)",
+                    );
+                }
+            }
+        }
+        assert!(
+            accent_border_cells > 0,
+            "the focused Tables panel must render accent-coloured border cells",
+        );
+
+        // With nothing focused (Input), no border cell wears the accent.
+        let mut app2 = App::new();
+        app2.tables = vec!["Customers".to_string()];
+        app2.nav_focus = NavFocus::Input;
+        let buf2 = render_to_buffer(&mut app2, &theme, 110, 24);
+        for y in 0..buf2.area.height {
+            for x in 0..buf2.area.width {
+                let cell = &buf2[(x, y)];
+                if is_border(cell.symbol()) {
+                    assert_ne!(
+                        cell.fg, theme.mode_simple,
+                        "no border cell may wear the focus accent when nothing is focused (at {x},{y})",
+                    );
+                }
+            }
+        }
+    }
+
     #[test]
     fn focused_tables_panel_scrolls_and_clamps() {
         // ADR-0046 DC3: more tables than fit → a large offset reveals the