risdr 0.3.1

CRAN release candidate

Added executable examples for the principal simulation, covariance, sufficient dimension reduction, prediction, slicing, structural dimension, and subspace-assessment workflows.
Hardened dependency, metadata, URL, spelling, and citation records for the first CRAN submission.
Declared both knitr and rmarkdown as vignette builders so that vignettes rebuild correctly when suggested packages are not pre-installed.
Added a package spelling dictionary and R-hub validation workflow.
Corrected structural-dimension examples to request an admissible maximum dimension directly, avoiding expected dimension-reduction warnings.
Excluded the repository-level CITATION.cff file from source-package builds while retaining inst/CITATION for the installed R package.
Retained the Zenodo DOI as the permanent identifier for the archived version 0.3.0 release and made the installed-package citation report the installed package version.
Completed local, GitHub Actions, pkgdown, coverage, URL, spelling, and selected R-hub checks successfully.

Promoted repeated predictive cross-validation and complexity-aware cross-validation to the exported API.
Added explicit cov_args, stabilization_args, and sdr_args controls to prevent component arguments from leaking into unrelated functions.
Improved prediction for one-row inputs, reordered named columns, and alternative structural dimensions.
Restricted the real-data workflow to its verified continuous-response scope.

Added ridge and Ledoit-Wolf covariance methods to central method validation.
Replaced the observation-wise Ledoit-Wolf accumulation loop with an algebraically equivalent vectorised calculation.
Vectorised the principal Hessian directions kernel calculation.
Strengthened integer, missing-value, covariance, slice, survival-indicator, and resampling validation.
Corrected rho = 0 handling for AR(1) simulation and guarded sparse-basis generation when the predictor dimension is small.
Added a user-supplied true-basis option and ensured that simulated training and test samples share the same central subspace.
Made projection matrices robust to non-orthonormal full-rank bases.
Return NA with a warning when MAPE is undefined because an observed value is zero.

Added five vignettes, a structured pkgdown configuration, a professional README, contribution guidance, issue templates, and release documentation.
Expanded the testthat suite across validation, covariance estimation, SDR kernels, prediction, dimension selection, resampling, simulation, plotting, and real-data helpers.
Added multi-platform R CMD check, test coverage, and pkgdown workflows.
Added selected supplied thesis outputs under inst/extdata as provenance fixtures. Legacy simulation prediction outputs are explicitly marked for targeted rerun because the original script regenerated the true basis in the test sample.
Added the supplied aligned EPI training and test matrices, with dimensions, column alignment, and SHA-256 provenance recorded in inst/extdata/README.md.
Added a configurable corrected reproduction script for Simulations A, B1, and B2. Corrected files use distinct names and do not overwrite legacy outputs.

The principal user-facing function names from the supplied baseline are retained.
Version metadata now records the agreed development release number, 0.3.0.