* clientupdate: return NOTREACHED for macsys
The work is done in Swift; this is now a documentation placeholder.
Updates #6995
Signed-off-by: Chris Palmer <cpalmer@tailscale.com>
* cmd/tailscale/cli: make `tailscale update` query `softwareupdate`
Even on macOS when Tailscale was installed via the App Store, we can check for
and even install new versions if people ask explicitly. Also, warn if App Store
AutoUpdate is not turned on.
Updates #6995