Refactor and enhance various components across the application

- Removed obsolete plans for stroke tuning, commit regression gate, and wxPlainSlider port.
- Updated scrollable panel functionality to include optional scrollbar visibility.
- Enhanced brush panel to filter brush styles by category for improved user experience.
- Adjusted canvas rendering logic to prevent UI freezes during active drawing.
- Modified stroke brush logic to allow single dab drawing at the current position when no movement occurs.

hcie-engine-api/src/stroke_brush.rs

@@ -98,11 +98,17 @@ impl Engine {
         if Self::is_specialized_style(tip.style) {
             if let Some((lx, ly, lp)) = self.last_stroke_pos {
                 if let Some(layer) = self.document.get_layer_by_id_mut(layer_id) {
+                    // If click without movement, draw a single dab at current position
+                    let points_vec = if (lx - x).abs() < 0.001 && (ly - y).abs() < 0.001 {
+                        vec![(x, y, pressure)]
+                    } else {
+                        vec![(lx, ly, lp), (x, y, pressure)]
+                    };
                     draw_specialized_stroke(
                         &mut layer.pixels,
                         layer.width,
                         layer.height,
-                        &[(lx, ly, lp), (x, y, pressure)],
+                        &points_vec,
                         tip.style,
                         tip.size,
                         tip.hardness,