* feat: add arch-updater plugin
* fix(arch-updater): declare shelled-out commands, close Flatpak ignore gap, surface real check failures
Address PR review: plugin.toml only listed pacman-contrib despite invoking
awk, sed, test, uname, pacman, sh, sudo, flatpak, xdg-open, yay and paru;
the Flatpak ignore list was enforced in the panel but not in the actual
`flatpak update`; and checkupdates/AUR/Flatpak checks piped through
awk/sed in a way that swallowed real command failures as an empty/clean
result instead of an error.
* fix(arch-updater): fix Luau long-string that broke service.luau parsing
The Flatpak ignore-filter awk snippet used a [[ ]] long bracket string,
but its own content ("skip[arr[i]] = 1") contains a literal ]] that
closed the string early, corrupting everything after it and failing
the whole file's parse (not just the Flatpak path). Switched to a
[=[ ]=] long bracket, which isn't terminated by a bare ]].
