Add Markdown support to the CSV directive

[theletterf]

This adds Markdown rendering support to the CSV include directive.

Some notes:

• NormalizeCsvCellMarkdown + IsPlainUrl: These exist because the main MarkdownParser.Pipeline doesn't include UseAutoLinks(). If we added .UseAutoLinks() to the pipeline, bare URLs would automatically become links and these two methods could be deleted. However, that's a global change that might affect other content unexpectedly.
• RenderInlineMarkdown: This avoids wrapping single-paragraph content in <p> tags inside table cells. Without it, **Bold** would render as <td><p><strong>Bold</strong></p></td> instead of <td><strong>Bold</strong></td>.

The most impactful simplification would be adding UseAutoLinks() to the main pipeline, which would eliminate NormalizeCsvCellMarkdown and IsPlainUrl entirely. The inline rendering optimization is CSV/table-specific.

Update
Removing autolinks as an exception from the PR so I can open a separate PR just for autolinks.
——

LLM disclosure: I've used GPT Codex 5.2 and Claude Opus 4.5 in Cursor.

[github-actions]

🔍 Preview links for changed docs

• docs/syntax/csv-include.md

[shainaraskas]

nice nice nice this is awesome

[Mpdreamz]

I am not opposed to adding autolink.

We should poll all docs tech leads.

[shainaraskas]

poll all docs tech leads

I wish we had it because mostly not having it introduces bugs for us (people putting in plain links without us noticing)

cc @florent-leborgne + @szabosteve

[reakaleek]

Is it working?

https://docs-v3-preview.elastic.dev/elastic/docs-builder/pull/2532/syntax/csv-include.md

The output shows an empty tag

  <csv-include>
  </csv-include>

---

// edit:

Ah, I just noticed.. this is about rendering markdown from CSV cells.

I guess I found a bug.

// edit 2:

• Fix csv-include LLM markdown and PlainText output #2536

[florent-leborgne]

Autolinks were the default in asciidoc and it was handy so people are used to it and I'm all for it, we'd just need to make sure it's deactivated where needed (code snippets & co)

[theletterf]

I'm removing autolinks as an exception from this PR to avoid mixing two features and will open a separate PR to add and test autolinks where it makes sense, if that's OK.

[theletterf]

@elastic/docs-engineering Moved the autolinks bits to #2541

With that, I think this one is ready for prime time!