Function runMotionPass

packages/cli/src/commands/layout.ts:400–419

* Motion verification (#1437): sample the asserted selectors on a dense grid * against the same seeked timeline the renderer uses, then evaluate the spec's * assertions in Node. Reuses the live page from the layout audit — no extra * Chrome launch. Findings reuse the LayoutIssue shape.

(
  page: import("puppeteer-core").Page,
  spec: MotionSpec,
  duration: number,
)

 * Chrome launch. Findings reuse the LayoutIssue shape.
 */
async function runMotionPass(
  page: import("puppeteer-core").Page,
  spec: MotionSpec,
  duration: number,
): Promise<{ issues: LayoutIssue[]; sampleCount: number }> {
  const times = buildMotionSampleTimes(spec.duration ?? duration);
  if (times.length === 0) return { issues: [], sampleCount: 0 };

  const { selectors, livenessScopes } = collectSamplingTargets(spec.assertions);
  const ambiguous = await findAmbiguousSelectors(page, selectors);
  if (ambiguous.length > 0) return { issues: ambiguous, sampleCount: 0 };

  const canvas = await page.evaluate(() => ({
    width: window.innerWidth,
    height: window.innerHeight,
  }));
  await page.addScriptTag({ content: loadBrowserScript("motion-sample.browser.js") });
  const frames = await collectMotionFrames(page, times, selectors, livenessScopes);
  return { issues: evaluateMotion(frames, spec.assertions, canvas), sampleCount: frames.length };
}

/** Read + validate the motion sidecar; print the error and exit on a bad spec. */
function resolveMotionSpec(specPath: string, json: boolean): MotionSpec {