Open one node of the maintained record (traversal, sb.node.v1)

To see how the record fits together, start at an entity or event (e.g. Hormuz) and traverse its maintained relationships; each step returns its relation type, receipts, standing and time. Walk the maintained record node to node. Returns ONE node in schema sb.node.v1 — an entity (e), a situation or corroborated claim (p), or a co-mention relation (r) — with its identity, five separate standing records, the knowledge cutoff it was read at, provenance (build), and its neighbours folded: children (observations, each with its source url) and relations (situations, claims and co-mentions it takes part in), each as a count plus the first page of typed refs and a cursor. Follow any ref's id, or pass a cursor, to open the next level. Same object as the MCP tool traverse. The same door also answers by query at GET /api/v1/node?id=… with a full id (sb:e/…), a starting point by name (entity:hormuz, event:strait-of-hormuz) or a cursor alone. Free, no key, CORS-enabled. PUBLISHED LIMITS (also stated in every node's limits): one level per call (depth must be 1; there is no whole-graph dump); pageSize 1-50, default 10; members listed up to 50; 60 calls a minute per caller (runaway-loop protection, not a meter); one knowledge cutoff, the deploy's. THREE STATES, NEVER TWO: a level we read and found empty has count: 0; a level we could not read has count: {state: "cannot-measure", reason}; a level the projection cannot hold has count: {state: "not-built", reason}. An unknown id is a 404 with code node_not_found; a store we could not read is a 503 cannot_measure (the node may exist). Version 1 is PROJECTED from today's graphs (build.plane), not read from the maintained world state. Claim ids are provisional (a wording change mints a new id); relation ids use the proposed letter r. Edge-cached 5 minutes.