False-positive `unintentional comparison` error with closures

### 🔎 Search Terms

unintentinal, comparison, 2367, overlap

### 🕗 Version & Regression Information

- typescript: `v7.0.2`
- node: `v24.14.1`
- pnpm: `v12.3.4`

### ⏯ Playground Link

_No response_

### 💻 Code

```ts
let n: "a" | "b" = "a";

const updateN = () => {
n = "b";
};

// This comparison appears to be unintentional because the types '"a"' and '"b"' have no overlap. [2367]
if (n === "b") {}

updateN();

// This comparison appears to be unintentional because the types '"a"' and '"b"' have no overlap. [2367]
if (n === "b") {}

n = "b";

// No error
if (n === "b") {}
```

### 🙁 Actual behavior

If a variable of type `"a" | "b"` is changed in a function with closure, the LSP fails to catch the change, and assumes that it was never changed.

### 🙂 Expected behavior

No error warning, since code works as expected

### Additional information about the issue

_No response_

Reproduce the closure example in the issue with TypeScript v7.0.2 and inspect the type-checker path that emits diagnostic 2367. Trace how control-flow narrowing is handled across updateN, then add a regression test covering both comparisons; done means the comparison after the closure call produces no false-positive warning while the example remains correctly checked.

Written by the indexing model from the issue text.