Set page.ai selector preferences once per Playwright project

UI libraries such as Headless UI, Radix, and AG Grid generate new element IDs on every render. page.ai already had a per-call option to stop recording ID-only selectors. Now a Playwright project can set it once for every test.

export default defineConfig({
  metadata: { volatileElementIds: true },
});

• volatileElementIds drops ID-only selectors so steps anchor on a test ID, a label, or text
• noSelectorFailover keeps only the most specific selector
• A per-call option still overrides the project default
• Applies when a step is recorded; existing cached steps keep their selectors until re-recorded