chore: 2026 upkeep

[schloerke]

Fixes #180

Summary

Addresses the 2026 upkeep checklist from usethis::use_tidy_upkeep_issue().

Done

• Add tidy GitHub labels (use_tidy_github_labels())
• Add Code of Conduct (use_tidy_coc())
• Add lifecycle infrastructure (use_lifecycle()); deprecate export(verbose=) with lifecycle::deprecate_warn()
• Add rlang standalone types-check (use_standalone("r-lib/rlang", "types-check")); replace stop() calls in quarto_ext.R with cli::cli_abort()
• Delegate assert_nzchar_string() to rlang::check_string(allow_empty = FALSE)
• Replace hand-rolled check in assets_remove() with check_character()
• Add Air formatter config (air.toml) and format-r-code: true in GHA routine job
• Fix broken URL in README.md (shinylive Python docs link)
• Add class = to unclassed expect_error() calls in tests
• Add assertion unit tests (27 tests in test-assertions.R)
• Fix R CMD check NOTEs: missing rlang imports, spelling wordlist, .Rbuildignore
• Run use_tidy_description()
• Update .Rbuildignore for .context and .git (worktree support)
• urlchecker::url_check() passes cleanly

Skipped (N/A)

• use_readme_rmd(): Keep README.md as-is (no .Rmd)
• use_tidy_style(): Handled by routine GHA job with format-r-code: true
• use_codecov_badge(): Not using codecov
• use_tidy_logo(): No logo exists for this package
• use_tidy_dependencies(): No compat files to replace
• use_package("R", "Depends", "4.1"): No pipe or \(x) syntax used in R/
• Switch to base pipe (|>): No pipe usage in R/
• Switch to base anonymous function (\(x)): Skipped
• Convert vignette chunk options: No vignettes directory
• use_tidy_github_actions(): Using shiny-workflows, not r-lib/actions
• build_readme(): No README.Rmd
• Re-publish released site: Will do after merge if needed

Already done (pre-existing)

• use_roxygen_md(), use_github_links(), use_pkgdown_github_pages()
• use_package_doc(), use_testthat(3)
• use_mit_license()
• pak::pak() in README
• R/ and test/ file names aligned
• No master → main issues
• Alt-text: no images in package
• cran-comments.md has no check environments section

Test plan

• devtools::check() passes with 0 errors, 0 warnings, 0 notes
• All 27 new assertion tests pass
• urlchecker::url_check() passes
• CI passes

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