flexstanr 0.1.0

Initial release: a portable Stan-backend layer that a Stan-based R package can fit its models through, using either rstan (default) or, optionally, cmdstanr.

• stan_options() collects and validates sampler options for the chosen backend, forwarding them verbatim and guarding against mixing one backend’s argument vocabulary into the other.
• fit_model() dispatches a fit to the backend recorded on the options and resolves the calling package’s compiled model automatically.
• Backend-agnostic accessors read a fit without knowing which backend produced it: backend_draws_array(), backend_extract(), backend_generate_quantities(), and backend_has_draws().
• use_flexstanr() wires flexstanr into a host package’s DESCRIPTION.
• cmdstanr is an optional backend, used only through requireNamespace() guards; rstan is the default and only hard Stan dependency.