Y-GATE TOPOLOGY AND THE GEOMETRIC ORIGIN OF BLACK-HOLE MASS (IX v6)

In the pregeometric FCD-RBv6 framework, the observed matter-antimatter asymmetry and the strictly left-handed chiral coupling of weak interactions are resolved without invoking ad-hoc CP-violating phases. We formalize the 5D geometry of the Y-gate manifold, a tri-coordinated junction embedded in an Anti-de Sitter (AdS_5) bulk possessing both spherical throat geometry and cylindrical symmetry along the extra-dimensional flux axis. The manifold comprises Mouth A (visible brane), Mouth B (CPT-conjugate mirror brane), and Mouth C (opening into the stochastic 5D AdS_5 bulk). We show that the orientation parameter Ω = ±1 acts as a topological switch governing the parity and mass-flow distribution between branes. The primary injection of mass-energy from the bulk during the Reversed Big Bang preserves global balance (B_total = B_A + B_B = 0). Furthermore, we demonstrate that the absence of right-handed neutrinos in the visible sector is a direct consequence of the primordial 1:7 Pauli-blocking bottleneck on the mirror brane, which geometrically polarizes the bulk chiral modes. Finally, we rigorously delineate the functional boundary between the thermodynamic bulk-exchange of the Y-gate and the localized topological confinement of the B_3 braid.