Global 'this' capture logic is slightly wrong in `--noImplicitThis`

@DanielRosenwasser đang làm issue này rồi.

Từ ngày 21/1/2026.

```ts
// @strict: true
function f(this: typeof globalThis) {
return () => this;
}
```

**Expected:** no error
**Actual:**

>The containing arrow function captures the global value of 'this'.

I think we just need to add an `isSourceFile(container)` check or something.