From Collinear Null Flow to Three-Channel Domain: A Pre-Closure Mechanism in Constrained Null Geometry

This work develops a pre-closure mechanism in Constrained Null Geometry for the emergence of an admissible three-channel domain. Starting from a collinear accumulated null flow P = A k, the paper identifies internal decompositions of the same external null flow and the corresponding kernel of invisible internal fluctuations. Recursive non-trivial fluctuations accumulate a phase trace and may reach a first-loss boundary, denoted as lom. The paper shows that lom does not by itself produce a closed three-channel domain. A rank-three post-lom regularization can generate triangle candidates, including proton-like Y3 proto-triangles, but the local edge-memory route obstructs the bare three-channel domain D3ch_bare. An electron-like boundary domain Ce does not close the proton-like structure directly. Instead, it acts as a domain enabler: it lifts the weak boundary/centrality pair and establishes the admissible three-channel domain D3ch. The supplementary reproducibility package contains the event-level numerical certificate, threshold manifest, verification scripts, and recomputed certificate output. The central certificate inequality is: max M_D3_bare = 0.5498361491 < tau_D3 = 0.72 < min M_D3_Ce_recipe = 0.7210474582. Thus the paper isolates the pre-domain step: A k -> ker dpi -> lom -> R3 -> Y3 proto-triangle -> Ce -> D3ch, while leaving the subsequent closed Y3, electron, photon, and hydrogen sectors to the previously developed CNG closure papers.