Initial release.

• EvalCase, EvalSuite, and EvalReport with Markdown and JSON output.
• Built-in checks: contains, notContains, matches, isValidJson, predicate, and LLM-as-judge scoring with Check.judge.
• ResponseCache interface in the core and a file-backed FileResponseCache in package:llm_eval/io.dart (atomic writes) for deterministic reruns in CI.
• Concurrent case execution with stable result order.
• Repeat runs with a flakiness rate.