Fix URL handling for tangled.sh and single-dot handles
- Add is_tangled_host function to handle both tangled.org and tangled.sh
- Fix domain_from_handle to require 2 dots (user.domain.tld format)
- Handles like "gazagnaire.org" now return the full handle instead of
incorrectly extracting "org" as the domain
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>