chore: import upstream snapshot with attribution

src/free_claude_code/cli/proxy_auth.py

@@ -0,0 +1,9 @@
+"""Shared proxy-auth policy for FCC client launchers."""
+
+PROXY_NO_AUTH_SENTINEL = "fcc-no-auth"
+
+
+def proxy_auth_token(auth_token: str) -> str:
+    """Return the configured proxy token or the no-auth client marker."""
+
+    return auth_token.strip() or PROXY_NO_AUTH_SENTINEL