perf: add performance test case

[hustcc]

性能测试已移至单独的 test/perf.test.ts 文件。

测试结果：

• 加载 100 个文档: 2379ms
• 平均每文档: 23.79ms

全部 126 个测试通过 ✓

[gemini-code-assist]

Code Review

This pull request introduces a performance test suite in test/perf.test.ts to benchmark loading 100 random documents into the Context. The review feedback correctly identifies a potential resource leak: if an assertion fails or an error is thrown during the test, ctx.close() will not be called, which can leave database connections open and cause cleanup failures in afterAll. It is recommended to wrap the context operations in a nested try...finally block to guarantee that ctx.close() is always executed.

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