Function encode_frame 

pub fn encode_frame<T: Serialize>(value: &T) -> Result<Vec<u8>, FrameError>

Encode a serializable value into a length-prefixed frame. Format: [4-byte big-endian length][JSON payload]

Errors

Returns FrameError::Oversized if the payload exceeds 10 MB, or FrameError::Json if serialization fails.