Replace the single CatanRuleSet with a set of expansions and add a scenario field; saves with the old ruleSet still decode. Setup shows a toggle per expansion and a map picker for Seafarers. Combining expansions is rejected for now (lifted in a later phase). Co-Authored-By: Claude Sonnet 5.5 <[email protected]> Claude-Session: https://claude.ai/code/session_01TWwLCrXa9aFVg8dZsCdLBZ