Summary
--

This addresses another discrepancy Codex noticed between `noqa` and `ruff:ignore` while reviewing my
`--add-ignore` PR. `noqa` had special handling for shebang lines, which allowed it to suppress a
diagnostic with a 0..0 range, like `D100`, even when a shebang was present that prevented putting
the suppression on the first line:

```py
 #!/usr/bin/python
 # noqa: D100
```

[Playground](https://play.ruff.rs/5381b897-06d1-4d41-900b-cc85a40b2740)

This was previously not the case for `ruff:ignore`.

```py
 #!/usr/bin/python
 # ruff:ignore[D100]
```

[Playground](https://play.ruff.rs/1d3dde25-2692-43f3-a6fb-54b2e156ba66)

Test Plan
--

A new mdtest covering this scenario

in the same section, this gets appended to the other code block and is no longer a shebang. in a
separate section, mdtest doesn't extract the trailing `# error` comment on the shebang line, so it's
impossible to assert that the error occurs