- Add types/api-responses.ts with ApiResponse<T>, PaginatedResponse<T> - Add types/errors.ts with comprehensive error type hierarchy - Replace all any usage (53 → 0, 100% reduction) - Add RawAPI response interfaces for type-safe mapping - Update catch blocks to use unknown with type narrowing - Add getState mock to chatStore tests Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>