`export { _void as void }` leads to exporting duplicate identifiers

### 🔎 Search Terms

`export void` `export reserved` `export null`

### 🕗 Version & Regression Information

- Reproducible since typescript v4. In older releases, it doesn't export anything. I also tried the latest dev release (5.9.0-dev.20250716)
- This is the behavior in every version I tried, and I reviewed the FAQ for entries about `exports`

### ⏯ Playground Link

[Playground (important: lang:javascript)](https://www.typescriptlang.org/play/?target=99&jsx=0&filetype=js#code/FAUwHgDg9gTgLgAgMZQHYGdEH0BuUCWAJggLwIDeAvsKJLIuQrgcQIboJ5EKUI1A)

### 💻 Code
Using the following `tsconfig.json`:

```json
{
"compilerOptions": {
"target": "esnext",
"lib": ["esnext"],
"module": "esnext",
"allowJs": true,
"checkJs": true,
"declaration": true,
"declarationMap": true,
"outDir": "./dist",
"emitDeclarationOnly": true,
"strict": true,
"noImplicitAny": true,
"moduleResolution": "bundler"
}
}
```

I compile declaration files for this code `${project}/schema.js` (only happens when compiling javascript):

```ts
const _null = {}
const $void = {}

export { _null as null, $void as void }
```

### 🙁 Actual behavior

The produced declaration file `schema.d.ts` is erroneous. It has duplicate identifiers:

```ts
declare const _null: {};
declare const $void: {};
export { _null as null, _null as null, $void as void, _void as void };
```

### 🙂 Expected behavior

No duplicate identifiers:

```ts
declare const _null: {};
declare const $void: {};
export { _null as null, $void as void };
```

### Additional information about the issue

For any reserved keyword, `tsc` always exports `_{reserved} as {reserved}`, whenever `{reserved}` is exported. Even though the variable `_{reserved}` does not exist.

It is only reproducible when compiling javascript.

先从提供的 tsconfig.json 和 schema.js 复现开始，然后检查 JavaScript 针对 export 列表的仅声明 emit。将生成的 schema.d.ts 与预期的 export 语句进行比较；当保留关键字 export 只出现一次，且没有不存在的标识符被 emit 时，即表示完成。

由索引模型根据 Issue 内容生成。