Fix malformed skewness/kurtosis formulas in vector function docs

[Copilot]

The documentation for kurtosis_vec() and skewness_vec() contained malformed math expressions (broken braces/parentheses and invalid symbols), which prevented correct rendering. This updates both formulas to valid LaTeX so the generated help output displays correctly.

• Roxygen source updates

  • Replaced malformed inline formula strings in R/vec-cumulative-functions.R with valid display-math \deqn{} expressions for both functions.

• Generated Rd sync

  • Updated man/kurtosis_vec.Rd and man/skewness_vec.Rd to match the corrected roxygen math output.

• Formula shape now documented as

  #' \deqn{\frac{\frac{1}{n} \sum (x - \mu)^4}{\left(\frac{1}{n} \sum (x - \mu)^2\right)^2}}
  #' \deqn{\frac{\frac{1}{n} \sum (x - \mu)^3}{\left(\frac{1}{n} \sum (x - \mu)^2\right)^{3/2}}}

[Copilot]

Pull request overview

This PR fixes malformed math expressions in the documentation for kurtosis_vec() and skewness_vec() so the formulas render correctly in the generated R help pages, improving the usability of these vector-statistics utilities within the RandomWalker package.

Changes:

• Replaced broken inline/backticked formula strings with valid LaTeX display-math using \deqn{} in the roxygen docs.
• Regenerated and committed the corresponding .Rd files to keep man/ output synchronized with roxygen source.

Reviewed changes

Copilot reviewed 1 out of 3 changed files in this pull request and generated no comments.

File	Description
R/vec-cumulative-functions.R	Updates roxygen documentation to use valid \deqn{} LaTeX formulas for kurtosis and skewness.
man/kurtosis_vec.Rd	Syncs generated Rd output to the corrected kurtosis \deqn{} formula.
man/skewness_vec.Rd	Syncs generated Rd output to the corrected skewness \deqn{} formula.

Files not reviewed (2)

• man/kurtosis_vec.Rd: Language not supported
• man/skewness_vec.Rd: Language not supported