Function assemble_lane_local_beat_kernel 

pub fn assemble_lane_local_beat_kernel(
    input: AssembleLaneLocalBeatInput,
) -> LaneLocalBeat

Assemble one canonical 512-bit lane-local output transfer.

Beats 0 through 32 contain two signature segments, beat 33 contains segment 66 followed by the public seed, and beat 34 contains only the public-key hash in its valid low half. Out-of-range indices return an invalid zero beat.