v0.12.0

• Added: reconcile mailing-list identities via Datatracker person id
• Added: message-citation graph and find_message_citations tool
• Added: find_related tool for nearest-neighbour search across a corpus
• Added: citation URLs on draft and charter chunks
• Added: norms for contributing to an IETF effort
• Changed: diversify search_corpus results by default with MMR
• Fixed: drop stale digests on empty re-gather
• Fixed: resolve body-form archive URLs in fetch_by_url
• Fixed: prune orphaned GitHub archives and issue dirs for untracked repos
• Removed: TODO.md (migrated to GitHub issues)