Bind shifted affine virtuals to source columns

[latifkasuli]

Goes towards #185, which blocks #91. Follow-up to #230.

This extends affine virtual Booleanity targets to forward-row-shifted sources:

• Shifted source pairs are deduplicated in public UAIR-signature order.
• The prover carries one evaluation per unique shifted witness source and appends signature-derived shifts over the existing alpha-prime-projected witness slots to multipoint evaluation.
• Shifted witness evaluations are absorbed before multipoint challenges and bound to committed source openings through the existing shift kernel and PCS chain.
• The verifier derives the exact witness-claim count from the public signature, recomputes shifted public sources directly, and reconstructs each expected affine endpoint from its shifted and unshifted terms.
• Per-prime families receive matching zero padding because affine virtual Booleanity targets remain in $Q[X]$.

Shifts at or beyond the trace domain now consistently represent the all-zero, zero-padded column in both the prover MLE selector and verifier shift predicate. The affine materializer also handles index overflow as an out-of-range row.

Affine virtuals remain uncommitted Booleanity targets, so shifted witness terms reuse existing committed source openings and add no PCS commitments. SHA-256/ECDSA UAIR adoption remains separate.

Tests cover shifted witness-only and public-only paths, interleaved public/witness ordering across two witness sources, first-occurrence deduplication and appended-source indices, signature-derived length rejection, tampered shifted claims, and shifts equal to or greater than the trace length.