Fix Markers layer button always enabled on load when layer was disabled (#1382)

* Initial plan

* Fix Markers layer button always enabled on load when layer is disabled

Agent-Logs-Url: https://github.com/Azgaar/Fantasy-Map-Generator/sessions/f076f8dd-0d93-423f-b87c-211b91f5dbc7

Co-authored-by: Azgaar <26469650+Azgaar@users.noreply.github.com>

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: Azgaar <26469650+Azgaar@users.noreply.github.com>

Author: Copilot

public/modules/io/load.js

@@ -456,7 +456,7 @@ async function parseLoadedData(data, mapVersion) {
       if (isVisible(labels)) turnOn("toggleLabels");
       if (isVisible(icons)) turnOn("toggleBurgIcons");
       if (hasChildren(armies) && isVisible(armies)) turnOn("toggleMilitary");
-      if (hasChildren(markers)) turnOn("toggleMarkers");
+      if (hasChild(markers, "svg")) turnOn("toggleMarkers");
       if (isVisible(ruler)) turnOn("toggleRulers");
       if (isVisible(scaleBar)) turnOn("toggleScaleBar");
       if (isVisibleNode(byId("vignette"))) turnOn("toggleVignette");

public/modules/ui/layers.js

@@ -829,7 +829,7 @@ function toggleMarkers(event) {
     if (event && isCtrlClick(event)) editStyle("markers");
   } else {
     if (event && isCtrlClick(event)) return editStyle("markers");
-    markers.selectAll("*").remove();
+    markers.html("");
     turnButtonOff("toggleMarkers");
   }
 }