Function splinter_shard_rebid 

pub unsafe extern "C" fn splinter_shard_rebid(
    shard_id: u32,
    intent: u8,
    priority: u8,
    duration_tsc: u64,
) -> c_int

@brief Refresh (re-bid) an existing claim’s window. Updates claimed_at to splinter_now() and optionally changes intent/priority/duration. This is the fairness re-bid: a shard that needs more time must re-bid rather than hold. @return 0 on success, -1 if shard_id holds no slot, -2 on bad args.