Scan outward for observed location-sensitive chart transitions

Calculates one exact birth moment at the supplied coordinates and eight equal radial checkpoints on each of eight fixed bearings, up to a caller-declared maximum radius. For Ascendant sign, Midheaven sign, all twelve cusp signs, and selected-planet houses, it returns the first observed checkpoint bracket on each bearing or an explicit no-transition or unavailable-geometry state. Brackets describe only consecutive sampled checkpoints; they do not prove the exact transition location, detect every intermediate transition, guarantee the unsampled disk, rank locations, rectify birth data, interpret a chart, or make predictions. Gauquelin is excluded because it is a 36-sector system. One standard quota unit per admitted request; failed or timed-out admitted attempts are not refunded. Do not automatically retry. Historical mode uses an explicit BCE/CE date object and UT1 conventions. Its response is the versioned historical envelope, not the modern UTC envelope. Read result for calculation fields and metadata for limits and uncertainty.