:sig
String gz_uncompress(String compressed)

:params
compressed : gzip-format compressed bytes
return value : uncompressed bytes

:see
>sys
gz_compress
zip_list
zip_extract

:content
Uncompresses a gzip-format byte string and returns the original content.

```uce
String compressed = file_get_contents("/tmp/hello.txt.gz");
String plain = gz_uncompress(compressed);
```

`gz_uncompress()` validates the gzip header, CRC32 footer, and uncompressed-size footer. It throws a runtime error when the input is not a supported gzip stream or fails validation.