docs: Phase 1 homepage cards (Memory, Protocol, Sites)

[reemsabawi-mystenlabs]

Summary

Phase 1 of the docs homepage revamp: simplifies the landing page to three product entry points.

• Cards reduced from four to three: Walrus Memory, Walrus Protocol, Walrus Sites (drops Console/Marketplace, adds Sites)
• Copy taken from the Phase 1 IA mockup; hero unchanged
• Product grid switched to three columns (stacks below 860px)
• Kept the existing icon treatment; screenshot thumbnails from the mockup are a planned follow-up

Stacked on jessie/new-work (PR #3474) so it folds into the homepage work rather than pulling that branch into main.

Open items

• Card screenshot thumbnails (need assets)
• "persists / persistent" wording on the Memory card + hero vs. the Unified Messaging guidance

[github-actions]

PR Preview Action v1.8.1
🚀 View preview at https://MystenLabs.github.io/walrus/pr-preview/pr-3506/
Built to branch gh-pages at 2026-07-01 15:43 UTC. Preview will be ready when the GitHub Pages deployment is complete.

[github-actions]

📋 afdocs check results

URL: https://MystenLabs.github.io/walrus/pr-preview/pr-3506/

Running checks on mystenlabs.github.io/walrus/pr-preview/pr-3506/...

Agent-Friendly Docs Check: https://MystenLabs.github.io/walrus/pr-preview/pr-3506/
Timestamp: 7/1/2026, 3:47:37 PM

content-discoverability
  ✓ llms-txt-exists: llms.txt found at https://MystenLabs.github.io/walrus/pr-preview/pr-3506/llms.txt
  ✓ llms-txt-valid: llms.txt follows the proposed structure (H1, blockquote, heading-delimited link sections)
  ⚠ llms-txt-size: llms.txt is 56,864 characters (between 50,000 and 100,000; consider splitting)
      Learn more: https://agentdocsspec.com/spec/#llms-txt-size
  ○ llms-txt-links-resolve: llms.txt contains 166 links, but none are under /walrus/pr-preview/pr-3506
  ○ llms-txt-links-markdown: llms.txt contains 166 links, but none are under /walrus/pr-preview/pr-3506
  ✓ llms-txt-directive-html: llms.txt directive found in HTML of all 173 pages, near the top of content
  ✗ llms-txt-directive-md: Could not fetch markdown for any of 173 pages; 173 had no markdown version
      Learn more: https://agentdocsspec.com/spec/#llms-txt-directive-md

markdown-availability
  ✗ markdown-url-support: No pages support .md URLs (0/173 tested)
      Learn more: https://agentdocsspec.com/spec/#markdown-url-support
  ✗ content-negotiation: Server ignores Accept: text/markdown header (0/173 pages return markdown)
      Learn more: https://agentdocsspec.com/spec/#content-negotiation

page-size
  ✓ rendering-strategy: All 173 pages contain server-rendered content
  ○ page-size-markdown: Skipped: dependency check did not pass
  ✓ page-size-html: All 173 pages under 50K chars (median 42K HTML → 8K markdown (80% boilerplate))
  ✗ content-start-position: 25 of 173 pages have content starting past 50% (worst 74%)
      Learn more: https://agentdocsspec.com/spec/#content-start-position

content-structure
  ✓ tabbed-content-serialization: 53 tab group(s) across 30 of 173 pages; all serialize under 50K chars
  ✓ section-header-quality: 2 page(s) with tab headers checked; headers include variant context
  ✓ markdown-code-fence-validity: All 0 code fences properly closed across 1 pages

url-stability
  ✓ http-status-codes: All 173 pages return proper error codes for bad URLs
  ✓ redirect-behavior: No redirects detected across 173 pages

observability
  ✗ llms-txt-coverage: llms.txt covers 0/165 sitemap doc pages (0%); 165 missing
      Learn more: https://agentdocsspec.com/spec/#llms-txt-coverage
  ○ markdown-content-parity: Skipped: dependency check did not pass
  ✓ cache-header-hygiene: All 174 endpoints have appropriate cache headers

authentication
  ✓ auth-gate-detection: All 173 pages are publicly accessible
  ○ auth-alternative-access: All docs pages are publicly accessible; no alternative access paths needed

Summary
  12 passed, 1 warnings, 5 failed, 5 skipped (23 total)

Full spec: https://agentdocsspec.com/spec/