Addendum v1.1: Combinatorial Uniqueness of the Projection Filter and Non-Uniqueness of Its Geometric Realization

This record contains Addendum v1.1 to the paper“Geometric Origin of the Fine-Structure Constant from Event Exclusion”. The addendum formalizes structural conditions that were implicitly requiredfor the derivation presented in v1.0, without modifying any numerical resultor theoretical conclusion. In particular, it proves that the projection filter induced by theS³ → ℝ³ projection with event exclusion is uniquely fixed at the level ofcombinatorial grammar as a 16-cell structure isomorphic to the 4-cube graph Q₄,while its geometric realization and measure assignment in ℝ³ are necessarilynon-unique. This separation between grammatical uniqueness and geometric non-uniquenessaccounts for observer dependence without affecting the universality of thederived constant, and prepares the ground for subsequent work on effectivequantities and dynamical emergence.