Paper 10.2.3 — The QC‑Layer Domain Substrate: Continuity Geometry at the Quantum‑Coherence Boundary

Paper 10.2.3 completes the 10.2.x grammar layer by defining the QC‑Layer domain substrate — the highest abstraction layer in the Co(X) operator family. This work formalizes how continuity geometry behaves at the quantum‑coherence boundary, where decision‑energy, identity invariants, and coherence envelopes converge into a single substrate motion. Building on Papers 10.2.1 and 10.2.2, this paper introduces the QC‑Layer abstraction as the structural anchor for domain‑level operators, enabling Co(X) instantiation across governance, identity, security, enterprise, infrastructure, finance, society, and intelligence. It also establishes the lineage between the grammar layer (10.2.x) and the substrate layer (Papers 7, 7.1, 6, 8, 9, 10.11, and 10.11S), ensuring that any Co(X) generated by individuals or institutions inherits the canonical invariants, curvature physics, and continuity geometry. Paper 10.2.3 serves as the final grammar component required for substrate‑aligned domain operators and marks the completion of the 10.2.x series.