postgresql_deploy_mode defaults to compose (Docker) and the admin password is
generated via a /root password-file lookup, both of which fail on a native
macOS deploy (no Docker, /root not writable). The role already ships a native
path (macos.yml, Homebrew postgresql@16). In the script's Darwin block, set
postgresql_deploy_mode=native and pass postgresql_admin_password directly
(highest-precedence extra-var, bypassing the /root lookup). Linux unchanged.
Documents TC-MAC-017.