Function element_packer_kernel 

pub fn element_packer_kernel<const P: usize>(
    clock_reset: ClockReset,
    input: PackerInput,
    q: ElementPackerQ<P>,
) -> (PackerOutput, ElementPackerD<P>)

Wiring for ElementPacker.

• input.start (with node 0): load the prefix and reset fill to P.
• input.valid: place the node at fill. If it crosses the word edge, emit the full word and keep the remainder; on node 67, emit the final partial word.
• Output: the registered word from the previous cycle; valid is forced low during reset.