feat: add sticky error-aware key mastery

Persist ranked-only mastery and use it consistently across progression, milestones, counts, and localized UI. Preserve mastery during history rebuilds, replay errors accurately, and generate replay-derived test profiles. Document the follow-up plan to remove the drill history cap.

src/ui/components/typing_area.rs

@@ -111,8 +111,7 @@ fn choose_cursor_style(colors: &crate::ui::theme::ThemeColors) -> Style {
     // REVERSED modifier so the terminal itself swaps fg/bg, which guarantees a
     // visible cursor in every colour scheme.
     if colors.text_cursor_bg() == Color::Reset && colors.text_cursor_fg() == Color::Reset {
-        return Style::default()
-            .add_modifier(Modifier::REVERSED | Modifier::BOLD);
+        return Style::default().add_modifier(Modifier::REVERSED | Modifier::BOLD);
     }
 
     let base_bg = colors.bg();