many improvements

src/FitComp.svelte

@@ -0,0 +1,12 @@
+<script>
+  import { useSvelteFlow } from "@xyflow/svelte";
+	import {nodes, auto} from './stores.js';
+
+  const { zoomIn, zoomOut, setZoom, fitView, setCenter, setViewport, getViewport, viewport } =
+    useSvelteFlow();
+
+	nodes.subscribe((n) => {
+		if ($auto) fitView();
+	});
+</script>
+<button>Fit</button>