fix: legend positioning when resizing with bottom center layout (#7254)

* Initial plan

* fix: legend positioning when resizing with bottom center layout

Co-authored-by: Alexzjt <9548248+Alexzjt@users.noreply.github.com>

* fix: restore accidentally deleted chartChangeSizePolar.svg snapshot

Co-authored-by: Alexzjt <9548248+Alexzjt@users.noreply.github.com>

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: Alexzjt <9548248+Alexzjt@users.noreply.github.com>
Co-authored-by: huiyu.zjt <Alexzjt@users.noreply.github.com>

Author: Copilot

__tests__/integration/api-chart-change-size-legend-bottom-center.spec.ts

@@ -0,0 +1,25 @@
+import { chartChangeSizeLegendBottomCenter as render } from '../plots/api/chart-change-size-legend-bottom-center';
+import { createNodeGCanvas } from './utils/createNodeGCanvas';
+import { sleep } from './utils/sleep';
+import './utils/useSnapshotMatchers';
+
+describe('chart.changeSize with legend bottom center', () => {
+  const canvas = createNodeGCanvas(640, 480);
+
+  it('chart.changeSize(width, height) should correctly position centered bottom legend', async () => {
+    const { finished, button, resized } = render({
+      canvas,
+      container: document.createElement('div'),
+    });
+    await finished;
+    button.dispatchEvent(new CustomEvent('click'));
+    await resized;
+    const dir = `${__dirname}/snapshots/api`;
+    await sleep(20);
+    await expect(canvas).toMatchDOMSnapshot(dir, render.name);
+  });
+
+  afterAll(() => {
+    canvas?.destroy();
+  });
+});