fromOrdinal

Decodes the ordinal a mode is flattened to for AIDL transport, or null when it names no mode this build knows.

The IPC boundary carries a bare int, and the two sides ship independently: a caller built against a newer SDK can send an ordinal this build has no entry for, and any app on the device can send an arbitrary one to the exported services. Indexing entries directly turns both into an exception on a binder thread, so decode through here and report the bad value instead.