FluxTTSEncoding: "linear16"

Audio encodings this plugin supports.

Deepgram Flux also offers mp3/opus/flac/aac/mulaw/alaw, but AudioByteStream expects raw PCM samples and the agents framework has no decode path, so this port only exposes linear16 (same restriction as the minimax plugin). The Python plugin accepts the compressed encodings on its batch path because its AudioEmitter decodes by mime type.