Add blog post: reasoning-based vectorless retrieval over the wiki

New post "Similarity Isn't Relevance: How Draft Retrieves Context by
Reasoning, Not Vectors" — explains tree-search retrieval over the OKF
knowledge wiki (navigate routing descriptions, descend matching subtrees,
terminate on coverage) versus top-k embedding similarity. No vector DB, no
chunking, fully traceable.

- web/blog/reasoning-retrieval/index.html: the post
- web/blog/index.html: post card at top of the list
- web/feed.xml: RSS item + lastBuildDate bump
- web/sitemap.xml: new URL + blog index lastmod bump

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PCYuQxnYefqsVGnbMMriXZ

Author: claude

web/blog/index.html

@@ -88,6 +88,15 @@ <h1>The <span class="gradient-text">Draft Blog</span></h1>
             </section>
 
             <section class="post-list">
+                <article class="post-card">
+                    <a href="reasoning-retrieval/" class="post-card-link">
+                        <p class="post-card-meta"><time datetime="2026-06-20">June 20, 2026</time> &middot; 7 min read</p>
+                        <h2 class="post-card-title">Similarity Isn't Relevance: How Draft Retrieves Context by Reasoning, Not Vectors</h2>
+                        <p class="post-card-excerpt">Vector search returns the chunks that <em>look like</em> your query. Draft's knowledge wiki returns the concepts that <em>actually matter</em> &mdash; by reasoning over a navigable table of contents instead of running a similarity search over embeddings. No vector DB, no chunking, no cloud &mdash; and a retrieval path you can audit.</p>
+                        <span class="post-card-cta">Read post <span class="post-card-cta-arrow" aria-hidden="true">&rarr;</span></span>
+                    </a>
+                </article>
+
                 <article class="post-card">
                     <a href="graph-engine-vs-grep/" class="post-card-link">
                         <p class="post-card-meta"><time datetime="2026-06-16">June 16, 2026</time> &middot; 10 min read</p>