feat: allow sampling from a directly specified multivariate distribution

[roninsightrx]

Summary

• Add means, sigma, and sd parameters to sample_covariates_mvtnorm() so callers can sample without needing observed data
• means + sigma: sample from the given distribution directly
• means + sd: construct a diagonal covariance (diag(sd^2)) and sample from it
• data is now optional; passing both data and means issues a warning that data is ignored
• Version bumped to 0.0.0.9001

Test plan

• means + sigma samples the correct number of rows/columns with correct names
• means + sigma recovers the specified mean at large n
• means + sd constructs diagonal covariance and recovers correct mean and SD at large n
• sd length mismatch raises an error
• means without sigma/sd raises an error
• data = NULL without means raises an error
• n_subjects missing when data = NULL raises an error
• Seed reproducibility works with the new path
• Warning is issued when both data and means are provided
• All existing tests continue to pass

🤖 Generated with Claude Code

[Copilot]

Pull request overview

This PR extends sample_covariates_mvtnorm() to allow sampling from a caller-specified multivariate normal distribution (via means + sigma or means + sd) without requiring observed input data.

Changes:

• Add means, sigma, and sd parameters and a new “direct specification” sampling branch.
• Make data optional; warn when data and means are both provided.
• Add test coverage for the new parameter combinations and bump package version to 0.0.0.9001.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 4 comments.

File	Description
R/sample_covariates_mvtnorm.R	Implements the new direct-specification sampling path and updates argument handling/docs.
man/sample_covariates_mvtnorm.Rd	Updates generated documentation for the new arguments and data = NULL behavior.
tests/testthat/test-sample_covariates_mvtnorm.R	Adds new tests covering direct distribution specification, errors, warnings, and seed reproducibility.
DESCRIPTION	Bumps package version.

Comments suppressed due to low confidence (1)

R/sample_covariates_mvtnorm.R:31

• Documentation mismatch: @param ... says additional arguments are passed to mvrnorm(), but this function calls mvtnorm::rmvnorm(). Update the roxygen text to reference the correct function so the generated Rd is accurate.

#' @param seed integer random seed passed to [set.seed()] for reproducibility.
#' Default `NULL` does not set a seed.
#' @param ... additional arguments passed to `mvrnorm()` function
#'

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.