fix svelte skeleton

tools/static-assets/skel-svelte/client/main.js

@@ -1,9 +1,26 @@
 import { Meteor } from 'meteor/meteor';
 import App from '../imports/ui/App.svelte';
+import { mount, unmount } from 'svelte';
 
+let app; // will hold the mounted instance
 
 Meteor.startup(() => {
-  new App({
-    target: document.getElementById('app')
-  });
-});
+  const target = document.getElementById('app');
+
+  // (Re)mount
+  app = mount(App, { target });
+
+  // Clean up on HMR so we don't double-mount
+  if (import.meta.webpackHot) {
+    import.meta.webpackHot.accept();
+    import.meta.webpackHot.dispose(() => {
+      if (app) {
+        // pass the instance you got from mount()
+        unmount(app, { outro: false }); // set outro:true if you want transitions
+        app = null;
+      }
+      // optional: clear target to be extra safe
+      target.innerHTML = '';
+    });
+  }
+});