flexhaz v0.5.1

Changes since v0.5.0

• JOSS paper (paper.md + paper.bib) — 984 words, 12 citations, all 8 required sections
• CONTRIBUTING.md — community contribution guidelines
• CODE_OF_CONDUCT.md — Contributor Covenant v2.1
• Updated CITATION.cff with paper title and release date
• Multi-platform CI (macOS, Windows, Ubuntu devel/release/oldrel)
• CRAN submission prep (cran-comments.md, portable test paths, @return on all exports)
• Removed stale inst/exp_dist.Rmd
• Improved exponential line visibility in reliability engineering vignette

Package Status

• R CMD check: 0 errors, 0 warnings, 1 note (benign)
• Test coverage: 99.47% (322 tests)
• CRAN: submitted, awaiting review
• JOSS: paper ready for submission

v0.5.0

Changes

• Added helper distribution constructors: dfr_exponential(), dfr_weibull(),
  dfr_gompertz(), dfr_loglogistic() with analytical hazard, cumulative
  hazard, score, and Hessian functions where available.
• Added diagnostic methods: residuals() (Cox-Snell and Martingale),
  plot() (survival, hazard, cumulative hazard), qqplot_residuals().
• Added density() method (alias for pdf).
• Added assumptions() method for listing model assumptions.
• Added kaplan_meier() internal utility for empirical survival estimation.
• Added support for left-censored observations (delta = -1).
• Improved numerical stability in log-likelihood computation.
• Removed femtograd dependency — users supply their own derivative functions
  via score_fn and hess_fn, or the package falls back to numDeriv.
• Extracted internal helpers (get_delta(), require_params(), get_params() with length validation).
• Removed dead eps field from constructor.
• Refined vignettes and landing page with motivation-first narrative.
• Renamed automatic_differentiation vignette to custom_derivatives.

Full Changelog: v0.2.0...v0.5.0