a11y: default and grid listings emit empty <a> when an item description contains a link (link-name) #15211

When a listing item description contains a link, default and grid listings render empty, focusable <a> elements. axe-core reports them as link-name, keyboard users tab onto invisible links, and part of the item is no longer a link to the item.

This is a regression from 1.7. With this website (_quarto.yml with project: type: website):

---
title: "Listing"
listing:
  - id: default-listing
    type: default
    contents:
      - path: https://example.com/article
        title: "Article"
        description: "Read the article, see the [docs](https://example.org/docs)."
  - id: grid-listing
    type: grid
    contents:
      - path: https://example.com/article
        title: "Article"
        description: "Read the article, see the [docs](https://example.org/docs)."
---

::: {#default-listing}
:::

::: {#grid-listing}
:::

Quarto 1.6.43 renders the description link as text, inside a single link to the item:

<div class="listing-description">
<a href="https://example.com/article" class="no-external">Read the article, see the <span>docs</span>.</a>
</div>

Quarto 1.10.19 keeps the description link, nested in the item link. The browser splits the nested anchors, so the item link is left empty, and in the grid listing the card link is closed before the description:

<div class="delink listing-description"><a href="https://example.com/article" class="no-external">
</a><p><a href="https://example.com/article" class="no-external">Read the article, see the </a><a href="https://example.org/docs">docs</a>.</p>

</a><div class="card-text listing-description delink"><a href="https://example.com/article" class="quarto-grid-link">
</a><p><a href="https://example.com/article" class="quarto-grid-link">Read the article, see the </a><a href="https://example.org/docs">docs</a>.</p>

The delink filter is there for this. It turns links inside a Div with the delink class into spans, so the whole description stays one link to the item:

It only matches Pandoc Divs. Up to 1.6 the templates wrote <div class="delink listing-description"> as HTML in the Markdown, which Pandoc parses into a Div. f9a5250 and 43ff451 (for #11758) moved it into a raw HTML block, so there is no Div anymore and the filter does nothing. The delink class is even left in the output, as the filter removes it when it runs.

We could write this container as a fenced div again (::: {.delink .listing-description}), keeping only the item link as raw HTML, like the ::: {.body} div the template already uses. This gives the 1.6 output back.

Description links not being clickable is intended, see #10814 where making them clickable is discussed as an option. The table listing is not affected, as its description is not inside a link.

Related: #14380, #15129, #15066 (other empty links in default listings), #9469 (its listing axe test excludes these empty links for now).