fix(mig): make site-managed hooks optional

[dholt]

Choose the smaller fix: remove the assumed default hooks path rather than ship service-management hooks that may not suit a deployment. Preserve explicit custom hooks, including paths containing spaces. Inert Ansible rendering regressions cover default, unset, empty, and explicit hook settings; the original implementation fails the relevant regression cases. Role lint, playbook syntax checks, local regressions, whitespace checks, and public sanitization pass. No GPU reconfiguration was performed.