ising-model

HTE: cut K range at round(2*ln n) -- past that the series diverges

HTE: add per-graph exact f(3,4,5) variant, plot side-by-side with asym

Add high-temperature expansion (HTE) estimator at h=0

Cleanup pass: drop scratch scripts, refresh coarse FEP, polish HTML note

Add dense-FEP baseline; fix ground-init basin alignment