feat(org-chart): implement expandable layout and multi-company navigation

Integrate P5-1B through P5-4 shared Core layout, collapse, zoom/pan/fit, company roots and keyboard accessibility. Include React/HTML examples, virtual 20/100/300 employee fixtures, focused checks and the additive data contract.

examples/org-chart/prepare.mjs

@@ -38,3 +38,5 @@ await writeFile(path.join(output, 'p1-fixture.js'), `window.OrgChartP1Fixture =
 const p1App = await readFile(path.join(example, 'p1-app.js'), 'utf8');
 await writeFile(path.join(output, 'p1-app-classic.js'), p1App.replace('export async function startP1', 'async function startP1'));
 console.log(`OrgChart HTML example: ${output}`);
+for (const file of ['expanded.html', 'expanded-app.js', 'expanded.css', 'data-expanded-small.json', 'data-expanded-medium.json', 'data-expanded-large.json'])
+  await cp(path.join(example, file), path.join(output, file));