Preflight: check node + the bundled probe script + Chrome detection.

Measure and/or screenshot a page in real local Chrome.

Args: url: full URL to probe (http/https/file) measure_js: in-page JS expression (IIFE returning an object) evaluated after load; its value comes back as measurements. Example that measures one element's real text width: (() => { const el = document.querySelector('#target'); if (!el) return null; const b = el.getBoundingClientRect(); const cs = getComputedStyle(el); return { x: Math.round(b.x), y: Math.round(b.y), w: Math.round(b.width), h: Math.round(b.height), usable_text_width: Math.round(el.clientWidth - parseFloat(cs.paddingLeft) - parseFloat(cs.paddingRight) - 2) }; })() viewport_w / viewport_h: emulated viewport (also set via Emulation.setDeviceMetricsOverride, so it holds regardless of the Chrome window size) screenshot: capture a PNG and return it as base64 login: "user:pass" - a JSON POST login executed IN the page context before measuring (httpOnly cookies are fine - the page fetch carries them). Requires the target app to have a JSON login API. login_url: login endpoint path, default /api/auth/login login_body: JSON template with %u / %p placeholders, default {"username":"%u","password":"%p"} timeout_ms: overall probe timeout

Returns: {ok, origin, viewport, login_status, measurements, png_base64}