Links seem to adjust one level too high.

My MKDocs Material site is hosted from an enterprise GitHub pages site at `https://host.corp/orgName/repoName`. This URL being the root of the docs site. I have a link in a snippet that looks something like below. Instead of rendering the link to `https://host.corp/orgName/repoName/#reporting-feedback`, it instead resolves to `https://host.corp/orgName/index.md#reportingFeedback`.

```YAML
feedbackInstructionsLink: |-
[reporting feedback](index.md#reporting-feedback)
```

When I look in the console, I see this warning that seems to indicate that it's stepping too far back when it adjusts the relative link. I've got absolute link validation set to `relative_to_docs`; but even disabling that setting doesn't seem to have any effect at all. I've also tried different variations in the path and picking different pages that are deeper in the `/docs` folder as a test, but they all generally behave the same way. The behavior is also the same running both locally and as deployed to GitHub pages.

```
WARNING - Doc file 'getting-started/setup/index.md' contains a link '../../../index.md', but the target '../index.md' is not found among
documentation files.
```

Is there something I'm doing wrong, or is this a bug?

Reproduce the issue with the shown feedbackInstructionsLink in a MkDocs Material site hosted under /orgName/repoName, both locally and on GitHub Pages. Trace the plugin's relative-link adjustment using the warning for getting-started/setup/index.md as the starting clue. Done means the link resolves to the repository site's root anchor without an incorrect index.md path or warning.

Written by the indexing model from the issue text.