Function compact 

pub fn compact(
    prep: &CompactPreparation,
    options: &CompactOptions,
) -> CompactResult

Run a compaction pass — render each frame slice through the pi-natives ported renderer (render_snapcompact_png) so the returned bytes are real PNG-encoded image data.

Errors propagate as Vec::new() for the offending frame (so the caller still gets partial results) and the failure is logged via tracing. This is the only compact surface — the old NoopRenderer / FrameRenderer / compact_with indirection has been removed: there is one renderer, and it always returns real bytes.