Remove all dead code and fix ESLint ignore warning; update ESLint config to use ignores property; all tests pass

Author: rgilks

.eslintignore

@@ -1,4 +1,4 @@
-const CACHE_VERSION = '1753518350586-local-v1.0.0';
+const CACHE_VERSION = '1753520577285-local-v1.0.0';
 const CACHE_NAME = `royal-game-of-ur-${CACHE_VERSION}`;
 const OFFLINE_URL = '/offline';