convert utility functions

[eeholmes-uw]

Context

Part of the roxygen2 migration. Issue #4 (NAMESPACE bootstrap) must be completed first.

Conversion rules (apply to all conversion issues)

• Read only the Rd file for content — do not invent or infer anything not in the Rd.
• Ignore the \usage{...} block — roxygen2 generates usage automatically.
• Preserve math macros exactly: \eqn{latex}{ascii} and \deqn{latex}{ascii} — do not convert to $...$.
• Keep \code{\link{fn}} cross-reference style as-is.
• Convert: \strong{x} → **x**, \emph{x} → *x*, \code{x} → `x`.
• \title{} → first roxygen line (no tag).
• \description{} → @description, \details{} → @details, \value{} → @return.
• \arguments{\item{name}{desc}} → @param name desc.
• \section{Title}{...} → @section Title:.
• \examples{} → @examples (preserve \dontrun{} exactly).
• \seealso{} → @seealso, \references{} → @references, \author{} → @author.
• \name{} → @name (only if different from the function name).
• \alias{} → @aliases (only if different from the function name).
• \keyword{internal} → @keywords internal and no @export.
• No \keyword{internal} → add @export.

Task

Three functions in R/utility_functions.R:

Rd file	Function	Exported?
man/zscore.Rd	zscore	Yes
man/ldiag.Rd	ldiag	Yes
man/match_arg_exact.Rd	match.arg.exact	No (\keyword{internal})

For each:

1. Read the Rd file.
2. Insert a roxygen #' block immediately above the function definition in R/utility_functions.R.
3. Delete the Rd file.

After all three conversions, remove these lines from R/zzz_roxygen_exports.R:

#' @rawNamespace export(zscore)
#' @rawNamespace export(ldiag)

Verification

Run devtools::document() then devtools::check(). Commit.