move cli functionality to a separate file

recipes.py

@@ -1,6 +1,5 @@
 from abc import abstractmethod
 import collections
-import sys
 from typing import Dict, List, Any, Optional, Self, Set
 import os
 import json
@@ -689,24 +688,3 @@ class Builder:
                 print("ERROR:", e)
                 return 1
         return 0
-
-
-def help() -> None:
-    print(f"usage: {sys.argv[0]} build DIR - build pages in DIR/out")
-    print(f"       {sys.argv[0]} -h        - show help")
-
-
-def main() -> None:
-    if len(sys.argv) == 2 and sys.argv[1] == "-h":
-        help()
-        sys.exit(0)
-    elif len(sys.argv) == 3 and sys.argv[1] == "build":
-        ret = Builder().build(sys.argv[2])
-        sys.exit(ret)
-    else:
-        help()
-        sys.exit(1)
-
-
-if __name__ == "__main__":
-    main()