Based on analysis of the official Mumble client source at ./mumble/.
Documents the CryptStateOCB2 encryption layer, legacy vs protobuf UDP
audio formats, ping formats, version negotiation, and the IV tracking
algorithm.
Key finding: barnard advertises version 1.3.0 which is below the 1.5.0
protobuf-introduction threshold, so the server sends us legacy-format
audio (type 0x80) inside the 1.5 crypto envelope.
