Checks GitHub's latest release tag against the running version — used by the interactive menu only (never by plumbing commands, which must stay network-predictable). The result is cached for a few hours so launches don't hit GitHub every time, and every failure path degrades to :unknown.
Summary
Functions
The release-asset name for this machine, or nil when unsupported.
Latest release version straight from GitHub (no cache), or nil.
Returns {:current, vsn}, {:update, current, latest}, or :unknown.