Changes in version 1.0.0                        

  - Initial CRAN release.
  - Core GP functions: gp_train(), gp_predict(), and formula interface
    gpss() with predict() method.
  - Regression discontinuity design via gp_rdd() and gp_rdd_plot().
  - Interrupted time-series design via gp_its() with optional placebo
    checks.
  - Multiple kernel types: Gaussian, Gaussian-linear,
    Gaussian-quadratic, Gaussian-periodic-linear, and
    Gaussian-periodic-quadratic.
  - Automatic bandwidth selection via kernel variance maximization.
  - Optional noise variance optimization via marginal likelihood.
  - Support for mixed continuous/categorical covariates.
  - Prior mean support for incorporating external predictions.
  - Companion paper: Cho, Kim, and Hazlett (2026), "Inference at the
    data's edge: Gaussian processes for modeling and inference under
    model-dependency, poor overlap, and extrapolation," Political
    Analysis, doi:10.1017/pan.2026.10032.