new neutral public runtime-build inputs:
BandInput, SensorInput, and HyperspectralLibraryInput
new coerce_sensor_input(...) helper to normalize canonical ids, custom
sensor payloads, and existing SensorSRFSchema objects
new build_mapping_runtime(...) entry point returning PreparedRuntime so
callers can construct reusable runtimes directly from in-memory arrays
without first exporting a SIAC package to disk