Fix MinimapView hitTest intercepting clicks when hidden

When showMinimap is false, MinimapView.isHidden is set to true but
the hitTest override did not check isHidden. Combined with empty
mouseDown/mouseDragged overrides, this caused the hidden minimap to
silently swallow all click events in its frame area (~140px on the
right side of the editor), preventing cursor placement.

Add an isHidden guard at the top of hitTest so hidden minimap views
return nil and let clicks pass through to the underlying text view.

Closes #370

Author: sanvibyfish

Sources/CodeEditSourceEditor/Minimap/MinimapView.swift

@@ -267,6 +267,7 @@ public class MinimapView: FlippedNSView {
     }
 
     override public func hitTest(_ point: NSPoint) -> NSView? {
+        guard !isHidden else { return nil }
         guard let point = superview?.convert(point, to: self) else { return nil }
         // For performance, don't hitTest the layout fragment views, but make sure the `documentVisibleView` is
         // hittable.