v10.17.0 — near-q=1 zeros of B (P2)

Three explicit zeros of B are certified (Arb, rigorous winding number) near e(1/13) and e(1/17), where the arc theorem's saddle mechanism does not apply. An oddness lemma is proved: the saddle heights near these roots of unity pair as +-V, with both members surviving for odd N and only one for even N. Whether the zeros actually accumulate at these points remains HEURISTIC and open; it needs an amplitude non-vanishing result and a uniform error bound, neither proved. No density result is claimed on this range. Reviewed by Reviewer AF (CORRECT, no fixes required).