Function batch_pp_on 

pub fn batch_pp_on() -> bool

MEMRA_BATCH_PP=0: rollback/A-B seam for the BATCHED stage split (pp2-batch 2026-08-06). Default ON — with the ppN door open the batched decode step takes its own stage split (decode_step_batch_ppn) exactly as the eager step does. Setting 0 sends the batched path back through the unsplit body, which under a sharded cross-device placement is then caught by refuse_unsplit_if_remote (the 28x peer-read regime) rather than run silently. Exists so the bit-identity gate can A/B split vs unsplit IN ONE PROCESS against the same loaded weights — read per step, never memoized, for that reason.