truncProxy 0.1.0

• Initial public package release.
• Added PQB_estimator() for proximal weighting estimation under dependent left truncation.
• Added PQB_IPCW_estimator() for IPCW-adjusted proximal weighting estimation under dependent left truncation and right censoring.
• Added compiled bridge-process routines based on Rcpp and RcppArmadillo.
• Added simulation-based examples, regression tests, and GitHub Actions R CMD check workflow.