feat: add download guide pages for anvil-cmg

[frano-m]

Summary

• Add four new guide sub-pages under /guides for AnVIL-CMG: Data Download Options, Dataset Manifest Download, curl Command Data Download, and Individual File Download
• Add nested guide sub-menu to AnVIL-CMG header navigation with responsive visibility (desktop shows "Guides" link, tablet/mobile expands sub-items)
• Convert all guide images to WebP format and render with <Figure /> component
• Map MDX hr to MUI Divider and add content styles for hr and pre + p spacing

Test plan

• Verify all four guide pages render at their URLs (/guides/data-download-options, /guides/dataset-manifest-download, /guides/curl-command-data-download, /guides/individual-file-download)
• Verify /guides overview page still renders
• Verify header nav shows "Guides" as a link on desktop, and expands to sub-items on tablet/mobile
• Verify all images render correctly in WebP format at full width
• Verify footnote link works on curl command page
• Verify other sites (HCA-DCP, LungMAP) are not affected (should 404 on guide sub-pages)

Closes #4757

🤖 Generated with Claude Code

[Copilot]

Pull request overview

Adds a new set of AnVIL-CMG “Download” guides under /guides, wires them into both the header navigation (responsive submenu) and the left-side guide navigation, and improves MDX rendering/styling for rules and spacing.

Changes:

• Added four new guide sub-pages under /guides/* and their corresponding MDX content for AnVIL-CMG.
• Updated AnVIL-CMG header navigation to include a responsive “Guides” submenu.
• Updated MDX rendering to map hr → MUI Divider, adjusted content spacing styles, and migrated guide images to WebP rendered via <Figure />.

Reviewed changes

Copilot reviewed 14 out of 31 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
site-config/anvil-cmg/dev/layout/navigationItem.ts	Introduces shared left-nav NavItem constants for the guides section.
site-config/anvil-cmg/dev/config.ts	Adds nested “Guides” submenu to the AnVIL-CMG header navigation with breakpoint-based visibility.
pages/guides/index.tsx	Adds left-side guides navigation to the guides overview page.
pages/guides/data-download-options.tsx	New Next.js page for the “Data Download Options” guide + left navigation.
pages/guides/dataset-manifest-download.tsx	New Next.js page for the “Dataset Manifest Download” guide + left navigation.
pages/guides/curl-command-data-download.tsx	New Next.js page for the “curl Command Data Download” guide + left navigation.
pages/guides/individual-file-download.tsx	New Next.js page for the “Individual File Download” guide + left navigation.
app/content/anvil-cmg/guides/data-download-options.mdx	Adds MDX content for data download options guide.
app/content/anvil-cmg/guides/dataset-manifest-download.mdx	Adds MDX content for dataset manifest download guide.
app/content/anvil-cmg/guides/curl-command-data-download.mdx	Adds MDX content for curl command download guide, including a footnote + rule.
app/content/anvil-cmg/guides/individual-file-download.mdx	Adds MDX content for individual file download guide.
app/content/common/constants.ts	Maps MDX hr elements to MUI Divider.
app/components/Layout/components/Content/content.styles.ts	Adds content styling for hr spacing and pre + p spacing.
app/components/common/Figure/figure.styles.ts	Import reorder (no functional change) alongside Figure usage in MDX.
public/guides/curl-command-download/single-dataset-download-08b.webp	Adds a new WebP asset used by the curl command guide.

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[Copilot]

Pull request overview

Copilot reviewed 14 out of 31 changed files in this pull request and generated 6 comments.

Comments suppressed due to low confidence (1)

pages/guides/index.tsx:23

• These pages render the 404 component when mdxSource is missing, but the route will still be statically generated and served with a 200 status. Since the PR description/test plan expects guide sub-pages to 404 for other sites (no MDX content), consider returning notFound: true from getStaticProps when getContentStaticProps indicates missing content, so Next.js serves a real 404 status for this route.

const slug = ["guides"];

export const getStaticProps: GetStaticProps = async () => {
  return getContentStaticProps({ params: { slug } }, "Guides");
};

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