stwo

tune(prover): UltraLow batch 1 MiB -> 16 MiB; drop DIRECT_MMAP_BATCH_FLOOR

feat(prover): tier ProverMemoryMode with SmoothedPeak + UltraLow

refactor(prover): drop env-var knobs for memory mode / budget

feat: improve spill diagnostics on mobile

chore: tighten prover helper APIs