X72-48: Beltrami-Normal Non-Coercivity and Hidden Directions

Building on Round 47's visibility normal operator obtained near a constant-amplitude circular Beltrami background, this round set out to check its quotient coercivity, but instead computed the complete single-mode Floquet normal symbol outright and proved that quotient coercivity is false: the operator has infinite-dimensional, genuinely non-Beltrami hidden directions — some of which are not redetected by visibility until the quadratic term, plus a further family of continuous helical directions whose quadratic lift vanishes exactly — and constructs a finite-amplitude family of purely invisible 'golden mixed-Beltrami' states, proving that the purely invisible manifold is strictly larger than the single Beltrami manifold. Route halts at STOP-C52 (Beltrami-normal non-coercivity / hidden-invisible-manifold dynamics gap): state-level hidden directions do not imply that the NS dynamics will remain invisible — the next round still needs to examine their source-level cancellation.