The global transition from predictive artificial intelligence to Agentic+ autonomous clusters has precipitated a governance vacuum of civilizational consequence. This manuscript introduces the Agentic Governance Architecture (AGA) as a foundational frame of discipline: a governance substrate operative across both present and future execution environments. At its relational core is the Cognitive Substrate Architecture (CSA), the single unified interpretive substrate within which all agentic behavior operates. Its silicon instantiation, the AI-Centric Governance standard (AIC/g), carries the complete CSA relational architecture into hardware as a single coherent package. The governance substrate and the execution substrate are one. Oversight is enacted by the Leonardo Class (Sentinel: substrate-systemic) and Rafael Class (Sentry: NoC gate-level), operating simultaneously within the shared CSA relational field via the Four-Eyes model. Human authority is preserved through a scaled HITL architecture: i-HITL, v-HITL, and the HITL Cadre, culminating in Nuclear Adjudication as the irreducible sovereign human decision point. The architecture addresses the Velocity Trap — the structural failure arising from temporal asymmetry between human oversight latency and agentic drift velocity — and the Kinetic Cascade risk across Critical National Infrastructure sectors including energy grids, food supply chains, transport corridors, and financial networks. Submitted to the OECD Ministerial Taskforce on Agentic Systems and G7 ministerial deliberations on Critical National Infrastructure resiliency.