Dynamics of a Self-Consistent Relational-Wave Closed System: From the Local Instability of the 90-Degree Relative Equilibrium to Inflation, Spontaneous Symmetry Breaking, Grassmann Geometry, Terminal Universality and Relationalism

Paper 0 (capstone) of the series "Foundations of Self-Consistent Relational-Wave Closed Systems" (10 papers). This capstone assembles the results established by Papers 1-9 into a single causal chain: (single-wave equation of motion) -> (90-degree self-consistent relative-equilibrium floor and its algebraic exact solution) -> (ignition qualification = unstable relative equilibrium) -> (inflation = exponential amplification of the linearly unstable mode, refined as the finite-time Lyapunov rate of the tangent cocycle) -> (spontaneous symmetry breaking and degenerate vacua) -> (plane switching on the Grassmann manifold Gr(2,M), 4D span with two nonzero principal angles) -> (terminal universality a_inf=sqrt(H/M), selective erasure of memory) -> (anonymity and relational invariants). Three unifying axes: A (unification of instability), B (memory and erasure), C (relationalism). Each section compresses to a claim plus a single reference to the corresponding foundational paper (cited by Concept DOI). Author: Noriaki Kihara (WF System Co., Ltd.), ORCID 0009-0004-6753-4020.