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