Function compaction_decode_step 

pub const fn compaction_decode_step(
    remaining_before: usize,
    decode_succeeded: bool,
    remaining_after: usize,
) -> CompactionDecodeStep

Classify one compaction batch-stream decode step.

A decode failure can never be mistaken for end-of-stream: completion is admitted only when no input remains, and a successful decode must consume at least one byte.