Listing feed: shortcodes in website.description are not resolved

[gordonwoodhull]

Bug description

Shortcodes used in website.description are not resolved in the listing feed XML output. The raw shortcode syntax appears in the <description> element of the generated RSS feed.

This is the same root cause as #14237 (shortcodes in website.title not resolved in llms.txt): websiteDescription(project.config) reads the raw YAML value without passing it through Pandoc's shortcode resolution.

Affected code: src/project/types/website/listing/website-listing-feed.ts:125

const feedDescription = options.description ||
    format.metadata[kDescription] as string ||
    websiteDescription(project.config) || "";

Steps to reproduce

quarto create project website issue-feed
cd issue-feed

Edit _quarto.yml:

project:
  type: website

website:
  title: "My Site"
  description: "A site about {{< env DEMO >}}"
  site-url: "https://example.com"
  navbar:
    left:
      - href: index.qmd
        text: Home

format:
  html:
    theme: cosmo

Create _environment:

DEMO="testing"

Create index.qmd:

---
title: "Posts"
listing:
  contents: "*.qmd"
  feed: true
---

Create post1.qmd:

---
title: "First Post"
date: "2024-01-01"
---

A post.

Then render and inspect the feed:

quarto render
grep '<description>' _site/index.xml

Actual behaviour

<description>A site about {{&lt; env DEMO &gt;}}</description>

Expected behaviour

<description>A site about testing</description>

Testing infrastructure note

There is currently no smoke-all test infrastructure for verifying feed XML content. Adding a test for this would require:

1. A new ensureFeedRegexMatches verify function in tests/verify.ts (similar to ensureLlmsTxtRegexMatches) that derives the .xml path from the HTML output path
2. Registering it in the verifyMap in tests/smoke/smoke-all.test.ts
3. A smoke-all test project under tests/docs/smoke-all/website/ with a listing + feed configuration

The existing tests/smoke/site/render-listings.test.ts only checks HTML elements, not feed content.