Model graph: one head block with a consistent gutter and rhythm

src/graph/index.ts

@@ -308,7 +308,9 @@ class GraphPage {
     this.help.appendChild(table);
     this.help.appendChild(el('p', '', 'Matches stay bright, the rest dims. Connections show when both ends match. Click an element for its details; drag to move it; scroll to zoom. Press / to type a query. Layered puts clients on the left and data on the right, with registries before and decisions after; Links switches the dotted decision and registry links between all of them and the selected element\u2019s only.'));
     this.main.append(this.canvas, this.side, this.help);
-    this.root.append(top, bar, this.main);
+    const head = el('div', 'ag-head');
+    head.append(top, bar);
+    this.root.append(head, this.main);
     document.body.appendChild(this.root);
     this.syncLabels();
   }