Add Codex app-server upgrade skill

scripts/start-codex-app-server

@@ -26,13 +26,14 @@ chmod 700 "$RUN_DIR"
 
 usage() {
   cat <<USAGE
-Usage: $0 <start|stop|status|check-updates> [options]
+Usage: $0 <start|stop|status|check-updates|check-upgrade> [options]
 
 Commands:
   start                Start codex app-server if it is not already running.
   stop                 Stop codex app-server and remove stale runtime files.
   status               Print whether codex app-server is running.
   check-updates [-y]   Check GitHub releases and optionally install the latest Codex binary.
+  check-upgrade [-y]   Alias for check-updates.
 
 Environment:
   CODEX_BIN            Codex executable to replace. Defaults to the codex found on PATH.
@@ -565,7 +566,7 @@ case "$cmd" in
     if [[ $# -ne 0 ]]; then usage; exit 2; fi
     status_server
     ;;
-  check-updates)
+  check-updates|check-upgrade)
     shift || true
     check_updates "$@"
     ;;