Fix documentation errors for CRAN

[louisaslett]

This pull request implements a fix for the "Lost braces" issues detected in the package documentation (.Rd files) by R CMD check and flagged by CRAN (see https://cran.r-project.org/web/checks/check_results_smoof.html)

Summary of changes

• Fix "Lost braces" documentation error (this was the primary objective of the R Dev Day task)
• I spotted other documentation errors with tools:checkRd and also fixed these:
  • "\title should not end in a period" (this is cosmetic but appeared a lot)
  • "Non-ASCII contents without declared encoding" (added UTF-8 encoding to cover the page range dash)

Context

This task was proposed by R Core developer Kurt Hornik as part of an initiative to improve CRAN package documentation. Packages with public repositories (GitHub, GitLab, Bitbucket) and a higher number of reverse dependencies were prioritised. This PR has been completed as part of an R Dev Day at the University of Warwick on 12 Sept 2025 (see r-devel/r-dev-day#110).

Suggested next steps

• Merge this PR to incorporate the fixes.
• Monitor subsequent CRAN checks to confirm the NOTE does not reappear.
• The following can be used to identify the issues with the documentation which initially triggered inclusion in the Dev Day task: list.files("man", full.names = TRUE) |> sapply(tools::checkRd).