feat(android-playground): add live XPath audit

[quanruzhuoxiu]

Summary

• add a live Android XPath audit mode to the existing Playground preview
• render tree-bound overlays, issue filters, node selection, and synchronized tree navigation
• add fresh recapture and a browser download flow for saving the complete audit report
• keep the existing Agent options and scrcpy preview lifecycle intact

Stack

• depends on feat(android): add accessibility XPath audit CLI and report #2892, which depends on feat(android): add standalone accessibility XPath audit core #2891
• contains only the live Playground UI and session integration relative to feat(android): add accessibility XPath audit CLI and report #2892

The three-PR stack is self-contained on main and does not rely on any other unmerged feature PR.

Validation

• pnpm exec nx run-many --target=test --projects=@midscene/android-playground,@midscene/playground-app --skip-nx-cache (104 tests)
• pnpm exec nx build android-playground --skip-nx-cache
• pnpm run lint