add trackHover toggle

- Corrected rectangle corner coordinates to accurately show (cx, ay) and (ax, cy)
- Removed unused Counter.svelte component

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

line-segment-intersection/src/App.svelte

@@ -76,20 +76,7 @@
     };
   }
 
-  function handleCanvasClick(event) {
-    // If we're about to turn off tracking, update position one last time
-    if (trackHover) {
-      const rect = canvas.getBoundingClientRect();
-      const mouseX = event.clientX - rect.left;
-      const mouseY = event.clientY - rect.top;
-
-      // Add half grid unit offset for snapping to closest grid intersection
-      userPoint = {
-        x: Math.floor((mouseX + GRID_SIZE / 2) / GRID_SIZE),
-        y: Math.floor((HEIGHT - mouseY + GRID_SIZE / 2) / GRID_SIZE)
-      };
-    }
-
+  function handleCanvasClick() {
     trackHover = !trackHover;
   }