The central charge of nilpotent-wedge strata in real so(p,q): existence laws, a forced cocycle=metric identity, and a one-parameter contraction (Geometry of the vacuum, floor −1)

For a wedge nilpotent (rank N = 2) in a real orthogonal Lie algebra so(p,q), the central extension of the radical of its centralizer carries a central 2-form on the Heisenberg module. We give the laws of this charge, signature-resolved: it is non-degenerate iff the stratum is deep (Witt index at least 2), its rank is 2(n-4), and a local density exists iff q is at least 2; under mixing the semisimple part acts symplectically; the parity of a surviving core is odd; and the multiset of Darboux types equals the core signature (p-2, q-2). A junction theorem shows the unique (up to scale, in rank 2) Levi-invariant antisymmetric form factorizes as symplectic tensor metric, so the extension is forced by invariance, not postulated. The engine of that factorization (the decomposition of the exterior square of a tensor product, and the up-to-scale uniqueness of the orthogonal and symplectic invariant forms) is classical and is cited, not claimed; the contribution is its signature-uniform deployment inside real so(p,q). Finally the single free scalar is a unit of length, and its zero limit is an Inonu-Wigner contraction of the deep (Heisenberg) branch into the soft (affine) branch, exhibiting the two branches as two ends of one family. Prime metric: no new knob. All statements are for wedge families over the enumerated signatures n at most 7 together with symbolic all-d derivations where named; the classical frames are cited with multiplicity zero. No physical reading of any object is made or implied.