Fix batch_to_affine to handle infinity points by skipping them in the
cumulative Z product chain. The comb table has infinity entries at
index 0 of each block (representing "no teeth set"), and the old code
multiplied by Z=0 which corrupted all subsequent Z products.
Re-enable the comb method for ecmult_gen: only 3 doublings + ~43 table
lookups vs GLV+wNAF's ~130 doublings + ~32 additions.
Performance improvement (x86_64 standalone):
pubkeyCreate: 54.4 µs → 17.0 µs (3.2x faster)
signSchnorr: 109 µs → 36.2 µs (3.0x faster)
signXOnly: 109 µs → 35.9 µs (3.0x faster)
verify/ECDH: unchanged (don't use comb)
https://claude.ai/code/session_011KVZhDcV2G7idNWEBz12GY
Claude
a13ad7d243