Elastic Membrane Cosmology 5.2: Spacetime Evolution, Environmental Implosion, and Geometrical Resonance in a Non-Isolated Framework

We propose a fundamental paradigm shift in cosmology, transitioning from particle-based reductionism to an environmental-dynamic framework. We define the (3+1)-dimensional spacetime as a dynamic membrane possessing intrinsic viscosity and surface tension, embedded in a five-dimensional Bulk characterized by a non-linear potential gradient. This framework unifies dark sector phenomena through the dynamic interaction between the manifold and its environment. Core mechanisms include: (1) Cosmic buoyancy derived from the Bulk Background Potential Field (BBPF), (2) Environmentally-Induced Nonlinear Collapse (EINC) explaining early hyper-growth and the "Black Hole First" scenario, (3) Trans-membrane Locking and Metric Wakes explaining rogue singularities, and (4) Geometrical Resonant Markers resulting from transient inter-universal couplings. We validate these mechanisms against 2025/2026 data, including the starless "Cloud 9" entity,the gas sea of SPT2349-56, and the stability of early-epoch quasars. Keywords: 5D Bulk Cosmology, Spacetime Viscosity, BH-First, EINC, Cloud 9, SPT2349-56,Metric Wake, Cavitation Limit, X17 Resonance, Non-Isolated Systems.