- add internal/version: resolve from the release ldflag, else the go build
info (module tag / vcs revision), else "dev"
- show the version on the boot banner and for `sif version`
- Makefile now stamps `make` builds via git describe (matching the release ci),
so local/go-install builds report a real version instead of "dev"
- patchnotes.ShowOnce skips pseudo/dev versions so non-release builds dont make
a doomed github call
- document sif version / sif patchnote / SIF_NO_PATCHNOTES in the readme + usage
vmfunc