Crawls are same-origin by default. Enable allow_subdomains to follow
sibling/child subdomains (blog.example.com from example.com), or
allow_external_links for full cross-origin crawling.
Root domain extraction uses a heuristic that handles two-part TLDs
(co.uk, com.au). Includes 5 unit tests for root_domain().
Bump to 0.3.12.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>