Fetch a single signal by id

Costs 1 token(s) per request. Returns exactly one signal by its id (the id from a signals result). An id that has since been folded into another event resolves to that event, and meta.merged_from_request says so. Plan-dependent: on a plan without the full event detail (Free) the reported facts beyond the casualty counts are withheld, and each of the collection reasoning (with the GEOINT score), the market reasoning, the full source list and the relations opens on its own per plan; plan_lock names what was withheld and plan_lock.section_plans the plan that opens each part — a null there means not shown, not unknown (the same rule as the app and the public event pages). signal.measured_same_place lists the measurements recorded at the same place close in time (or, for a measured event, the reports there) — stored by fixed rules, never a confirmation; every plan sees that a pair exists and its kind, the times and the place name need the full event detail.