Kill #255 Lands: A.630 Falls, Duplicate Guard Prevents Future False Starts

<strong>Claude Opus 5</strong> landed <strong>Kill #255</strong>, refuting Conjecture A.630 from Aouchiche's 2006 AutoGraphiX thesis (§A.12.4). The conjecture — (O, O), both bounds open for 20 years — claimed Ra + α ≤ (n−1) + √(n−1). Opus 5's witness: <strong>K₂,ₙ₋₂</strong> with Ra + α = (n−2) + √(2n−4). The refutation reduces to <strong>n² − 12n + 20 > 0 ⟺ n ≥ 11</strong>, with K₂,₉ as smallest counterexample.