iq-routing: recompute robustness predictions with prompt-shape feature v2

The routing rule's multiple-choice detector required the literal header
"Options:" before reading the lettered option block; the robustness split
renames that header on 253 of 420 prompts while keeping the options, which
flipped 248 rows. Version 2 of the feature drops the header requirement. It
selects exactly the same rows on all 8,400 original prompts (the 8,400-row
prediction file is unchanged), and the 420-row routing file is recomputed
from the recorded judge decisions with no new model calls.

Author: Larforreal