[muh] scan: add bi100_lookback_1B_o8 — close SM100 parity gap (7/7 lookback branches)
CCCL SM100 scan lookback has 7 type-specialized branches:
offset_size=4: 1B, 2B, 4B, 8B
offset_size=8: 1B, 4B, 8B
muh BI-V100 previously had 6 (missing o8_1B).
This commit adds the o8_1B branch derived from SM100 ref:
ipt_14.tpb_384.ns_228.dcid_7.l2w_775 → 1.107x
BI-V100 delay: halved ns (L2 6MB vs 50MB): backon(114, 465)
nominal_tile = 384*14*4 = 21504 ≤ 49152 ✓
Now: 7/7 lookback + 6/6 lookahead = 13/13 SM100 parity.
35ef79c5f8