Scalar-Derived Gauge Closure of the QDL–SO10–1 Benchmark: Explicit Threshold Blocks, Dynkin-Index Accounting, and the v0.3 Closure Test

The QDL-SO10-1 grand-unification sequence defines a closure-first SO(10)-compatible benchmark within the Quantized Dimensional Ledger (QDL) program. Papers #1-#3 established the initial benchmark trilogy: a fixed SO(10)-compatible benchmark, its low-energy phenomenology, and a stress-test / robustness audit. Paper #5 began the executable hardening sequence by revising the gauge-closure target to inverse alpha_U = 44.501718, corresponding to alpha_U = 0.022471, and by converting the remaining Pati-Salam channel splittings into calibrated high-scale threshold targets. This paper supplies the v0.3 scalar-threshold hardening layer. The derivation is explicitly block-level: it proves that the calibrated v0.2 offset…