Refactor FancyCursor to use mouseover delegation

- Moves expensive DOM checks (`closest`) and class toggling from `mousemove` loop to `mouseover` handler.
- Removes `document.elementFromPoint` fallback to eliminate layout thrashing.
- Updates tests to verify performance improvements.
- Fixes `Hero.test.tsx` missing jsdom environment.

src/components/layout/FancyCursor.test.tsx

@@ -86,26 +86,22 @@ describe('FancyCursor', () => {
         document.body.removeChild(link);
     });
 
-    it('uses fallback elementFromPoint if hoveredElement is null', () => {
+    it('does not call elementFromPoint on mousemove', () => {
         // Reset elementFromPoint mock
         const mockElementFromPoint = vi.fn();
         // @ts-ignore
         document.elementFromPoint = mockElementFromPoint;
 
-        // We need to remount to reset internal state if any.
-        // However, 'hoveredElement' variable was defined INSIDE the component in my edit.
-        // Let's double check that.
-
         render(<FancyCursor />);
 
-        // Trigger mousemove WITHOUT prior mouseover.
-        // This should trigger the fallback.
+        // Trigger mousemove
         fireEvent.mouseMove(window, { clientX: 10, clientY: 10 });
 
         act(() => {
             vi.runAllTimers();
         });
 
-        expect(mockElementFromPoint).toHaveBeenCalledWith(10, 10);
+        // Should NOT be called in the optimized version
+        expect(mockElementFromPoint).not.toHaveBeenCalled();
     });
 });