Brings in the Katan rules engine, board, model and AI (WALA-119), its 51 unit tests and docs/RULES-catan.md. Only conflict was docs/README.md, which the GitHub-lineage migration had dropped: kept the engine branch's index and pointed the CI link (docs/CI.md no longer exists) at the root README. Co-Authored-By: Claude Sonnet 5.5 <[email protected]> Claude-Session: https://claude.ai/code/session_01JdMNbY5hLR7FjtfEE712xG