_on_verify_success() was missing _nickserv_complete() call, causing
_go_ready() to hang at _nickserv_done.wait() when registration
completed immediately (no email verification needed).
get_pending_registration() was not returning verify_url from the DB,
so _resume_pending_verification() never restored self._verify_url --
breaking cross-session captcha resume for OFTC-style networks.
Four regression tests added.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>