feat(editor): dock the sim panel and refit the canvas to the rest

The results panel floated over the canvas and hid the lower part of the
diagram. Dock it beneath the canvas instead, and refit the view when it
opens or closes so the whole diagram stays framed in the height that
remains. The refit fires on Vue Flow's `dimensions` (post-measure), not
on the toggle, so it frames against the settled size.

src/components/ResultsPanel.vue

@@ -59,9 +59,7 @@ const chart = computed(() => {
 </script>
 
 <template>
-  <div
-    class="absolute inset-x-3 bottom-3 z-30 rounded-box border border-base-300 bg-base-100/95 p-3 shadow-lg backdrop-blur"
-  >
+  <div class="shrink-0 border-t border-base-300 bg-base-100 p-3">
     <div class="flex items-center gap-2">
       <span class="text-sm font-semibold">Behaviour over time</span>
       <span class="truncate text-xs text-base-content/50">{{ store.model.name }}</span>