feat(help): header-driven --help for system-info functions

gip, gip4, gip6, ports, swapstat, sbver and steam-dl. All ignored $argv,
so --help previously ran the query or the launcher. sbver keeps its own
--brief flag: only argv[1] is inspected and --brief is not a help flag,
so the body still runs for it.

functions/gip4.fish

@@ -13,5 +13,7 @@
 # EXAMPLE
 #   gip4
 function gip4 --wraps='curl' --description 'Get public IPv4 address'
+    __fish_help_header (status current-function) $argv; and return 0
+
     curl -4 -s https://icanhazip.com
 end