Open page and read digest

Navigate to a URL and get the semantic DIGEST (~2-3KB): landmark regions with ids, headings with their section, and the top-15 RANKED actionables with complete absolute hrefs in structuredContent (only prose abbreviates them; privacy rules still apply). PDF links include a document hint with URL, title, evidence and source observation/id for an external PDF reader. A successful application/pdf response returns document {type, mediaType, url, title, source?, reader, textExtracted: false}, instead of pretending its text was observed; source retains the prior observation/id/title/href when an exact current link supplied the destination. Navigation metadata includes requestedUrl, finalUrl, navigationUrlsSanitized: true (navigation query values and opaque payloads remain hidden), and redirectChainAvailable. When available, redirectChain lists observed HTTP response URLs/statuses, with redirectChainScope: http, redirectChainTotal and redirectChainTruncated; client-side navigations are reflected by finalUrl, never invented as HTTP redirects. Ids (n_xxx) expire on every new observation. A top entry with placeholder: true is an EMPTY form field whose name is its placeholder — a prompt, never data from the site. Every observation reports authState and cookiesForOrigin: this tool drives ITS OWN isolated per-session BrowserContext, cookie jar and storage. authState is conservatively unknown; a cookie count is evidence, not proof of identity, because authentication can also live in storage, bearer state or the URL. For a task that needs the real signed-in session from another browser, this is the wrong instrument. If the site answered with a bot-mitigation interstitial, structuredContent carries blocked: true and challenge {vendor, reason, status, signal, and vendors when more than one is detected — vendors chain, and a confidently wrong name is worse than unknown for per-vendor retry routing}: the content was WITHHELD, which is a different answer from a page that has little on it — fall back to another fetcher rather than recording an empty result. A request that never reached an HTTP response returns failure {layer: dns|tls|transport|http, code, hostUp} instead of a thrown string — a DNS or certificate failure is neither a block nor an empty page. The open waits (bounded) for window.onload AND briefly watches the fresh document for timer-delayed first paints (entry ads armed via setTimeout at parse time), so late overlays/modals enter the FIRST digest; if the document is STILL not complete, structuredContent carries loading {readyState, waitedMs} and the prose says so — treat the digest as a truthful walk of an UNFINISHED page and re-observe before trusting completeness. Returns observationId (opaque identity of this observation) in structuredContent, and digest (marks/heads/top) in both structuredContent and prose — read the fields, do not parse the text. After a SAME-ORIGIN navigation, structuredContent may also carry carried: which strong-identity elements (data-testid / authored accessible names) persisted from the previous page and how their state/content moved (the cart badge "1"→"2"), plus only-before/only-after COUNTS of page-specific content — those counts are "different page", never removals/additions. Optional redact: session privacy rules — any name/label/text/state string containing a listed term leaves every observation as [redacted], and each observation carries an attestation that the policy ran (policyRevision, rulesActive) — never hit counts, which would tell you whether and how often the hidden term occurs. Raw form values are never returned; sensitive categories use coarse change signals and declare same-bucket uncertainty.