A few correct examples that the level doesn't deem correct

- This one should pass level 17, but doesn't: `(λabcd.ad)pyyp`.
- This one should pass level 18, but doesn't: `(λx.i)xλj.k`.

FWIW, the inspector thinks they're both beta-irreducible, despite reducing them.

复现 issue 中的两个示例：level 17 的 `(λabcd.ad)pyyp` 和 level 18 的 `(λx.i)xλj.k`。首先跟踪 level 检查路径和 inspector 的 beta-reduction 结果，然后验证这两个示例在其 reduction 完成后都能被接受。

由索引模型根据 Issue 内容生成。