RCD 2.0 — Paper P3 v1.0: Axisymmetric Solver for the Derived Galactic Sector — Quasi-Static Reduction and Operational Closure

Paper P3 v1.0 of the Radial Coherential Dynamics (RCD) 2.0 program. Constructs the axisymmetric solver for the galactic sector derived in P2 v1.0 and closes P3-O1 by reducing the nonlocal stress-energy tensor T_mu,nu^{conf} to a local quasi-static source. The reduction adopts the resummed (strong) version with full Gaussian saturation, yielding a nonlinear dependence on lambda = l_K |nabla C| / C_* through the functions F_1(lambda) and J_tr(lambda). The effective source density rho_conf = -mu^4 [2 F_1(lambda) + J_tr(lambda)] is negative-definite, a nontrivial prediction of the theory. The coupled system (modified Poisson equation plus nonlinear scalar field equation) is operationally specified with computable, tabulable source functions, boundary conditions, diagnostic observable v_c(r), and four kill switches. No numerical results are reported; this is the mathematical specification document. The precise Einstein-source identification remains as open problem P3-O1-bis.