Verifies a web UI in a running browser by measuring the live DOM with bundled scripts — visibility, clickability, alignment, overflow, and the state a click leaves behind — instead of reading screenshots. Use when a change to a web UI needs verifying in the running app, when a UI bug is reported (something on screen is missing, misplaced, clipped, or unclickable), or when acceptance criteria describe on-screen behaviour. Prefer this over writing custom Playwright page.evaluate code. Not for visual appearance (colors, fonts, spacing), cross-browser behaviour, or accessibility checks.