fix(deps): drop ggpubr for cowplot; unbreaks R-CMD-check on oldrel-2

[eliotmcintire]

Unblocks #34, #35 and every other PR: the ubuntu-latest (oldrel-2) leg has failed on every branch since late July, and it is not caused by any of them.

The failure is not what it looks like

The visible error is a vignette failure, but that is downstream:

derive_simplif.cpp:376:28: error: ‘R_ClosureFormals’ was not declared in this scope
ERROR: compilation failed for package ‘Deriv’
...
Error in loadVignetteBuilder(pkgdir, TRUE) :

Deriv 4.3.0 was published 2026-07-23 — a month after this repo's last green run (development, 2026-06-21). It uses R_ClosureFormals, an R >= 4.5 C-API entry point, while declaring only Depends: Rcpp with no minimum R version. So it builds on the R 4.5.x legs and fails to compile on oldrel-2's R 4.4.3. The dependency install aborts, the vignette builder is never installed, and rcmdcheck then dies in loadVignetteBuilder().

That explains the whole pattern: devel / release / oldrel-1 (all R 4.5.x) pass, oldrel-2 (R 4.4.3) fails, and it presents as a vignette error on a package whose vignette was not the problem.

Why we were pulling in Deriv at all

fireSenseUtils → ggpubr → car → pbkrtest → doBy → Deriv

ggpubr was used in exactly one line of the package:

# R/DEoptim_fns.R:267
invisible(ggpubr::ggarrange(plotlist = ff))

ff is a plain list of ggplots. cowplot::plot_grid() takes the same plotlist argument, and cowplot was already a Suggests — already used by plot_summaries.R (:323, :329) behind a requireNamespace() guard.

The change

• R/DEoptim_fns.R: ggpubr::ggarrange(plotlist = ff) → cowplot::plot_grid(plotlist = ff)
• DESCRIPTION: drop ggpubr from Imports; move cowplot Suggests → Imports

Removes 14 packages from the dependency tree: ggpubr, car, carData, pbkrtest, doBy, Deriv, lme4, quantreg, SparseM, MatrixModels, nloptr, minqa, abind, Formula.

No NAMESPACE or roxygen change — both packages were used via ::, neither had an @importFrom.

Notes

• The one behavioural difference to check on review: plot_grid()'s default spacing/alignment is not identical to ggarrange()'s. visualizeDE() arranges parameter histograms, so this is cosmetic, but it is a real difference rather than a pure no-op.
• The requireNamespace("cowplot") guard at plot_summaries.R:185 is now redundant (cowplot is an Import). Left in place — harmless, and out of scope here.
• Not addressed: Deriv's missing R (>= 4.5) constraint is an upstream CRAN bug and worth reporting to its maintainer, since it will bite anything else on R 4.4.