CSF-CMT vΩ.25.2: Tripartite Scope Partition of Mechanics — Meta-Field Wave Dynamics, Quantum Mechanics, and Classical Mechanics by Coarse-Graining Scale

Quantum mechanics is not a universal theory. This paper establishes a rigorous tripartite partition of mechanical applicability based on the coarse-graining scale L_c within the Cosmic String-Field and Coarse-Graining Meta-Theory (CSF-CMT). Layer I (L_c \sim l_{\text{string}}): meta-field wave dynamics governing the first-space initial state \Psi_I^{(0)}, where no particle concept, Hilbert space, or probability interpretation exists. Layer II (l_{\text{string}} \ll L_c \ll L_{\text{macro}}): standard quantum mechanics as an emergent effective theory, where particles arise as coarse-grained excitations and the Heisenberg uncertainty relation manifests as an information-cutoff effect. Layer III (L_c \to \infty): classical mechanics and deterministic geometry. The atomic horizon r_{AH} is identified as the physical boundary between Layer I and Layer II. This partition resolves the century-old quantum-classical boundary problem by demonstrating it to be a natural phase transition in coarse-graining scale, not a mysterious wave-function collapse.