Resolve a coordinate to its IANA timezone and return the current UTC offset, local wall time, DST status, and short abbr

Resolve a coordinate to its IANA timezone and return the current UTC offset, local wall time, DST status, and short abbreviation. Query: lat (-90..90), lon (-180..180), at (optional ISO 8601 instant; defaults to now). Returns { tz, abbreviation, offsetMinutes, offsetHours, localTime, observesDst, isDst, januaryOffsetMinutes, julyOffsetMinutes, instant, source }. Polygon lookup against a CC0 timezone boundary index; offsets and DST come from the runtime tzdata so transition rules stay current. Use when scheduling for a coordinate, converting timestamps to local wall time, or checking whether a location is currently observing daylight saving.