P70: Symmetry Algebra of the ρc Surface in CCEGA — Virasoro ⋉ BMS₃ Decomposition and Central Charge Ratio (e−1)²

We investigate which symmetry algebra reproduces S_ρc = e · S_Bek (P69) via the Cardy formula. A single Virasoro sector with c = e · c_GR gives only √e · S_Bek. Reproducing e · S_Bek exactly requires a two-sector decomposition: S_ρc = S_Virasoro + S_BMS₃ = S_Bek + (e−1) · S_Bek. The central charge ratio is c_BMS/c_Vir = (e−1)² ≈ 2.952. The BMS₃ sector arises from the RS1 extra dimension and is absent in GR. Falsifiable prediction: the QNM spectrum exhibits two frequency families with ratio f_BMS/f_Vir = e−1 ≈ 1.718, testable with Einstein Telescope. All results are exploratory; central charges are not derived from first principles.