831092841e
The two genuinely-missing arithmetic primitives (Mul = two-stream f64 product, Sqrt = one-input f64 root, negatives clamped to 0). They are the building blocks for the volatility stop as a composition (rolling EWMA stddev), replacing the fused VolStop node. Also corrects plan 0066 Task 3 (the VolStop removal must migrate its stage1_r_e2e.rs caller — a false premise the implementer caught). refs #117 #119