pathintdid 0.1.0

• Initial CRAN release.
• Ported from the community-contributed Stata package (pathintdid.ado, pathintdidplot.ado, pathintdidrobust.ado) to R.
• pathintdid(): cumulative causal effect (sigma), path-integrated ATT (tau-bar), and conventional static DiD, with cluster-style standard errors, t-tests, and confidence intervals.
• pathintdidplot(): two-panel base-graphics visualization of the treated/counterfactual paths and the running cumulative effect.
• pathintdidrobust(): dynamic placebo test for pre-treatment parallel trends, grid-density/quadrature-scheme sensitivity check, and anticipation-robust bounding estimator.
• Bundled example data set trainingpanel.