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/Editor.vue

@@ -24,7 +24,7 @@ import {
   VueFlow,
   type XYPosition,
 } from "@vue-flow/core"
-import { computed, onBeforeUnmount, onMounted, ref, useTemplateRef } from "vue"
+import { computed, onBeforeUnmount, onMounted, ref, useTemplateRef, watch } from "vue"
 import { useAutosave } from "@/composables/useAutosave"
 import { usePlayback } from "@/composables/usePlayback"
 import { parseModel, serializeModel } from "@/model/io"
@@ -74,6 +74,7 @@ const {
   getSelectedEdges,
   viewport,
   vueFlowRef,
+  dimensions,
   fitView,
 } = useVueFlow("meadows")
 
@@ -89,6 +90,26 @@ onNodesInitialized(() => {
   fitView({ padding: 0.2 })
 })
 
+// Docking the results panel (Simulate) shrinks the canvas; closing it gives the
+// space back. Re-fit either way so the whole diagram stays framed in whatever
+// height remains. Vue Flow re-measures the pane a frame after the panel
+// mounts/unmounts and republishes the size via `dimensions`; fitting on *that*
+// signal (not straight after the toggle) frames against the settled size, so the
+// diagram never lands jammed against the new edge. The flag scopes the fit to
+// panel toggles, leaving ordinary window resizes to Vue Flow's own handling.
+let fitOnResize = false
+watch(showResults, () => {
+  fitOnResize = true
+})
+watch(
+  () => [dimensions.value.width, dimensions.value.height],
+  () => {
+    if (!fitOnResize) return
+    fitOnResize = false
+    fitView({ padding: 0.2 })
+  },
+)
+
 // Restore the last document on mount and persist every change (F7). Arm the same
 // post-measure fit a load uses; fitting synchronously in onRestore would frame
 // against unmeasured 0×0 nodes, landing the restored model jammed top-left.
@@ -460,7 +481,6 @@ onBeforeUnmount(() => {
       <LoopOverlay />
       <GlossPanel />
       <Inspector />
-      <ResultsPanel v-if="showResults" @close="showResults = false" />
 
       <!-- Self-dismissing teaching hint, e.g. when a Flow is dragged back onto its
            own Stock to "close the loop". Click to dismiss early; z-30 keeps it above
@@ -479,5 +499,10 @@ onBeforeUnmount(() => {
         </div>
       </div>
     </div>
+
+    <!-- Docked beneath the canvas (not floating over it): opening Simulate shrinks
+         the canvas to the space above, where the diagram re-fits (see the
+         `dimensions` watcher in <script>). -->
+    <ResultsPanel v-if="showResults" @close="showResults = false" />
   </div>
 </template>