Add `markdown-link-check` with `pre-commit` to check for dead links in Markdown files

https://github.com/tcort/markdown-link-check

https://github.com/tcort/markdown-link-check?tab=readme-ov-file#run-as-a-pre-commit-hook

```
- repo: https://github.com/tcort/markdown-link-check
rev: ...
hooks:
- id: markdown-link-check
args: [-q]
```

We will need a config file with various rules:

https://github.com/tcort/markdown-link-check?tab=readme-ov-file#config-file-format

Start with the markdown-link-check README sections linked in the issue, especially “Run as a pre-commit hook” and “Config file format.” Determine the repository’s pre-commit configuration location, add the hook and its required rules, then run the configured pre-commit checks against Markdown files and confirm dead links are reported as intended.

Written by the indexing model from the issue text.