X72-49: Hidden Invisible-Manifold Source-Lock and Golden Transversality

Building on the golden mixed-Beltrami purely invisible manifold found in Round 48, this round directly tests whether state-level cancellation on that manifold also implies source cancellation. The result proves that the viscous source is exactly tangent at the golden-ratio root, but the nonlinear source is nonzero under any nontrivial mixing, so visibility erupts with an exact positive second-order curvature — meaning the entire golden hidden manifold, apart from the pure-Beltrami axis, is not a genuine NS-invariant branch, ruling out the first deep finite-amplitude hidden candidate family. Route halts at STOP-C53 (hidden-state / nonlinear-source transversality gap): state-level hiddenness does not imply dynamical hiddenness, handed to the next round to linearize source cancellation and build a systematic classification over the entire invisible manifold; this round also includes a numerical-verification script.