Paper T33b: Triplet Collapse and Pointer Basins in the Holosphere Lattice Triplet-Sector Implementation of Coherence Filtering, Measurement, and Thermalization

This paper completes the measurement layer of the Holosphere framework by providing a concrete physical mechanism for collapse, decoherence, and classical behavior in the triplet sector. Prior work established that physical states evolve on an SU(2) geometry and that observed outcome frequencies follow a cosine-squared law justified by symmetry and coherence filtering. What remained open was how a single definite outcome arises in an individual measurement without invoking a special observer rule. We model particles as stabilized triplet composites of three coupled internal modes. Two modes form a local readout pair, while the third acts as an anchor that maintains corridor compatibility during transport. Long-range quantum correlations persist as long as required links along a coherence corridor satisfy a strict admissibility gate. Measurement occurs when routing would require gate-violating links inside an apparatus-coupled region. At that point, deterministic descent into a detector-defined pointer basin occurs. This basin capture terminates corridor compatibility and produces a definite outcome. Decoherence is the finite-speed propagation of this compatibility loss, and thermalization corresponds to a high-rate regime of repeated basin capture events that erase corridor memory. The framework reproduces the standard low-strain cosine correlation limit while predicting structured deviations when links approach the gate threshold or when detector geometry biases basin structure. These predictions are distinct from path-memory effects identified in earlier work and from network-scale percolation limits developed in the membrane layer of the theory. The result is a scale-separated, falsifiable mechanism in which measurement is a structural transition in a discrete rotating lattice rather than an axiom.