Final one. `fetch()` rejects Base64 `data:` URLs containing percent escapes. For example, `%3D` should become `=` before Base64 decoding, but celld passes it straight to `atob()`.

Here is a minimal repro:

```js await (await fetch("data:text/plain;base64,YQ%3D%3D")).text(); // Should return "a", but throws InvalidCharacterError ```

Here is a patch

[0001-Percent-decode-Base64-data-URL-payloads.patch](https://github.com/user-attachments/files/32133835/0001-Percent-decode-Base64-data-URL-payloads.patch)