docs(concepts): explain content addressing as free versioning

[reemsabawi-mystenlabs]

Adds a Content addressing and versioning section to Walrus Fundamentals (docs/content/system-overview/core-concepts.mdx), explaining how a content-derived blob ID gives immutable versioning for free. Prose only, per the Sui docs style guide.

BEDU-603

What's new

• A content-derived blob ID means every version is its own blob (nothing overwritten), lineage is an ordered list of blob IDs, identical content dedups automatically, and a blob ID is tamper-evident proof of content for provenance and reproducibility.
• Version with a manifest blob: the pattern of keeping a small manifest blob mapping logical names to per-version blob IDs, where updating appends a new entry pointing at the new content-addressed blob.

Open questions for reviewers

1. Scope of the property vs. Quilt: the dedup / immutable-versioning behavior holds for regular blobs and for a quilt as a whole, but not for individual items inside a quilt (their QuiltPatchId is not content-derived). This section stays at the blob level. Should I add an explicit cross-reference/caveat tying this to the Quilt page (pairs with PR 1's third question)?
2. Section placement: added as a new top-level ## section at the end of the page. If you'd prefer it nested under an existing section or placed earlier (for example, right after the intro that introduces blob immutability), say where and I'll move it.
3. blob ID vs BlobId: used prose "blob ID" to match this page's existing style; the Quilt/client pages use the inline-code BlobId/QuiltPatchId forms. Flagging in case you want one convention across pages.

[jessiemongeon1]

Style Guide Audit

All 1 file(s) pass the style guide audit.

[github-actions]

PR Preview Action v1.8.1
Preview removed because the pull request was closed.
2026-06-17 21:37 UTC

[github-actions]

📋 afdocs check results

URL: https://MystenLabs.github.io/walrus/pr-preview/pr-3471/

Running checks on mystenlabs.github.io/walrus/pr-preview/pr-3471/...

Agent-Friendly Docs Check: https://MystenLabs.github.io/walrus/pr-preview/pr-3471/
Timestamp: 6/17/2026, 9:11:45 PM

content-discoverability
  ✓ llms-txt-exists: llms.txt found at https://MystenLabs.github.io/walrus/pr-preview/pr-3471/llms.txt
  ✓ llms-txt-valid: llms.txt follows the proposed structure (H1, blockquote, heading-delimited link sections)
  ⚠ llms-txt-size: llms.txt is 54,726 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 160 links, but none are under /walrus/pr-preview/pr-3471
  ○ llms-txt-links-markdown: llms.txt contains 160 links, but none are under /walrus/pr-preview/pr-3471
  ✓ llms-txt-directive-html: llms.txt directive found in HTML of all 167 pages, near the top of content
  ✗ llms-txt-directive-md: Could not fetch markdown for any of 167 pages; 167 had no markdown version
      Learn more: https://agentdocsspec.com/spec/#llms-txt-directive-md

markdown-availability
  ✗ markdown-url-support: No pages support .md URLs (0/167 tested)
      Learn more: https://agentdocsspec.com/spec/#markdown-url-support
  ✗ content-negotiation: Server ignores Accept: text/markdown header (0/167 pages return markdown)
      Learn more: https://agentdocsspec.com/spec/#content-negotiation

page-size
  ✓ rendering-strategy: All 167 pages contain server-rendered content
  ○ page-size-markdown: Skipped: dependency check did not pass
  ✓ page-size-html: All 167 pages under 50K chars (median 41K HTML → 8K markdown (80% boilerplate))
  ✗ content-start-position: 24 of 167 pages have content starting past 50% (worst 71%)
      Learn more: https://agentdocsspec.com/spec/#content-start-position

content-structure
  ✓ tabbed-content-serialization: 53 tab group(s) across 30 of 167 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 167 pages return proper error codes for bad URLs
  ✓ redirect-behavior: No redirects detected across 167 pages

observability
  ✗ llms-txt-coverage: llms.txt covers 0/159 sitemap doc pages (0%); 159 missing
      Learn more: https://agentdocsspec.com/spec/#llms-txt-coverage
  ○ markdown-content-parity: Skipped: dependency check did not pass
  ✓ cache-header-hygiene: All 168 endpoints have appropriate cache headers

authentication
  ✓ auth-gate-detection: All 167 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/