feat(orgchart): integrate chart-only viewport and scoped guard fixes

Add initial fit and direct wheel zoom with preserved default presentation. Integrate five scoped GuardFix findings and AI generation preselection policy. Exclude Cell experiments and retain five historical guard failures.

examples/org-chart-chart-only/react.tsx

@@ -0,0 +1,31 @@
+import { StrictMode, useMemo, useState } from 'react';
+import { createRoot } from 'react-dom/client';
+import { OrgChart } from '@hm-design/org-chart-react';
+import { JsonOrgChartDataSource } from '@hm-design/org-chart';
+import engineUrl from '@hm-design/org-chart/engine.css?url';
+import coreUrl from '@hm-design/org-chart/style.css?url';
+import { datasets, readQuery } from './data';
+import './chart-only.css';
+
+const { data, layout, embed } = readQuery();
+if (embed) document.body.classList.add('embed');
+const stylesheetUrls = { engine: engineUrl, core: coreUrl };
+let replace: (key: string) => void = () => {};
+let rerender: () => void = () => {};
+
+function ChartOnlyPage() {
+  const [key, setKey] = useState(data);
+  const [, setTick] = useState(0);
+  replace = setKey;
+  rerender = () => setTick(value => value + 1);
+  const dataSource = useMemo(() => new JsonOrgChartDataSource(datasets[key]!()), [key]);
+  // Inline option literals are intentional: equal values must not refit on re-render.
+  return <OrgChart dataSource={dataSource} stylesheetUrls={stylesheetUrls} displayMode="readOnly" layoutMode="auto"
+    autoLayout={{ type: layout }} presentationMode="chart-only"
+    zoom={new URLSearchParams(location.search).has('verify-min') ? { min: 0.8 } : undefined}
+    style={{ height: '100%' }} />;
+}
+
+createRoot(document.getElementById('chart')!).render(<StrictMode><ChartOnlyPage /></StrictMode>);
+// Verification seam only.
+Object.assign(window, { replaceData: (key: string) => replace(key), rerenderPage: () => rerender() });