Rebuilds the PEST++ invocation layer. PESTO's shell-out had never run: control
variables were passed as /h :name=value, which PEST++ has never accepted.
Fifteen defects, all present since the initial release (9 Apr 2026) and
shipped in every release since -- surfaced by grounding the layer against the
USGS sources and then the real pestpp 5.2.16 binary.

Verified: suite 522/0/0 with the binary present; end-to-end inversion recovers
k1=4.998, k2=1.001 against truth (5, 1); R CMD check --as-cran green on CI
(the local WARNING is Apple clang on R's own Boolean.h).