Validate Packets
Validate intermediate packets against their Pydantic schemas.
CLI Usage
acl-packet validate input/
Validates all four intermediate packets (transcript_packet.v1.json,
diarization_packet.v1.json, acoustic_packet.v1.json,
visual_packet.v1.json).
Exits 0 on pass, 1 on schema errors, 2 on missing required packets.