The proxy->bool refactor (770574f) missed the shared CLI test fixture, which
still used proxy: {caddy: {path_prefix: ...}} — failing ~25 CLI tests with
'Input should be a valid boolean'. Set it to proxy: True.
Also drop the now-dead 'caddy' entry from _STRUCTURAL_KEYS (no nested caddy
key exists anymore) and refresh a stale proxy.caddy docstring reference.