The inner-message codec is used on broker and client paths, but its current ByteBuffer routines trust…

The inner-message codec is used on broker and client paths, but its current ByteBuffer routines trust…: a task in MiMo-V2.6-RL-harbor-code: MiMo-V2.6-RL Code (Harbor) (Harbor dataset). Keep the existing compact frame format and successful behavior: encodeMessage/encodeMessages must preserve flags…