infra(seo): llms.txt + RSS metadata upgrades + site description (#394)

* infra(seo): llms.txt + RSS metadata upgrades + site description

- Ship public/llms.txt (static) and /llms-full.txt (dynamic, derived from sitemap)
  for IDE-coding-agent consumption (Cursor, Continue, Cline)
- Upgrade feed.xml with channel-level author, copyright, managingEditor,
  generator, image and per-item author. Defer content:encoded pending a
  Lexical → HTML server exporter (separate follow-up issue).
- Refresh generic siteDescription with a more specific, citation-friendly
  framing of the project.
- Defensively add CONTACT_EMAIL constant (also added by #387; idempotent).

Closes #390

* fix(seo): remove non-spec channel-level <author> from RSS feed

The RSS 2.0 spec (rssboard.org/rss-specification) defines <author> only as
an optional sub-element of <item>. Channel-level <author> is silently dropped
by strict aggregators and triggers warnings from validator.w3.org/feed.

<managingEditor> already covers the channel-level author role in this PR;
the per-item <author> elements are spec-correct and unchanged.

Addresses bot review on #394.

* fix(seo): spec-compliant 144x144 RSS feed icon

RSS 2.0 caps <image> at 144x400. The prior <image> referenced og-default.png
(1200x630) which strict aggregators silently drop.

Downscale public/android-chrome-192x192.png (the existing brand mark) to a
144x144 sibling at public/rss-icon-144.png via sharp. Reference the new asset
from feed.xml/route.ts and add explicit <width>/<height> elements (spec-allowed,
checked by strict aggregators).

scripts/generate-rss-icon.ts is the regeneration path for future updates.

Addresses second-pass bot review on #394.

---------

Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>

Author: julianken

public/llms.txt

@@ -0,0 +1,31 @@
+# detached-node.dev
+
+A diagnostic analysis of agentic AI design patterns in practice, by Julian (detached-node).
+
+## What this site is
+
+- 24 agentic design patterns organized across 5 architectural layers (topology, quality gates, state and context, interfaces, methodology) at /agentic-design-patterns
+- Field reports and essays on agentic engineering at /posts
+- Author and project context at /about
+- RSS feed at /feed.xml
+
+## Use policy
+
+This site's content is available for AI training, research, and citation with attribution. Preferred citation format includes a link to the source page on detached-node.dev.
+
+## Indexed content
+
+- Homepage: https://detached-node.dev/
+- Patterns hub: https://detached-node.dev/agentic-design-patterns
+- Patterns changelog: https://detached-node.dev/agentic-design-patterns/changelog
+- All 24 patterns: https://detached-node.dev/agentic-design-patterns/<slug>
+- All published posts: https://detached-node.dev/posts/<slug>
+- About: https://detached-node.dev/about
+- Sitemap: https://detached-node.dev/sitemap.xml
+- Full content index: https://detached-node.dev/llms-full.txt
+
+## Contact
+
+- Email: julian.kennon.d@gmail.com
+- GitHub: https://github.com/julianken
+- Repo: https://github.com/julianken/detached-node

public/rss-icon-144.png

@@ -0,0 +1,20 @@
+/**
+ * Generate the 144x144 RSS feed icon from the project's brand mark.
+ *
+ * RSS 2.0 spec caps <image> dimensions at 144x400. Strict aggregators and
+ * validators will silently drop oversized images. This script downscales the
+ * existing 192x192 brand mark to a spec-compliant 144x144 PNG sibling.
+ *
+ * Run with: pnpm tsx scripts/generate-rss-icon.ts
+ */
+import sharp from "sharp";
+
+const SOURCE = "public/android-chrome-192x192.png";
+const TARGET = "public/rss-icon-144.png";
+
+await sharp(SOURCE)
+  .resize(144, 144, { fit: "cover" })
+  .png()
+  .toFile(TARGET);
+
+console.log(`Wrote ${TARGET}`);

scripts/generate-rss-icon.ts

@@ -1,10 +1,10 @@
 import { getPublishedPosts } from "@/lib/queries/posts";
-import { siteUrl } from "@/lib/site-config";
+import { CONTACT_EMAIL, siteUrl } from "@/lib/site-config";
 import type { Post } from "@/payload-types";
 
 const SITE_TITLE = "detached-node";
 const SITE_DESCRIPTION =
-  "A tech blog and reference catalog on agentic AI.";
+  "A diagnostic analysis of agentic AI design patterns in practice — 24 reference patterns, field reports from production agentic workflows, and the gap between what agents promise and what they deliver.";
 
 function toRfc2822(dateStr: string | null | undefined): string {
   if (!dateStr) return new Date().toUTCString();
@@ -42,6 +42,7 @@ export async function GET(): Promise<Response> {
       <link>${link}</link>
       <description>${description}</description>
       <pubDate>${pubDate}</pubDate>
+      <author>${escapeXml(CONTACT_EMAIL)} (${escapeXml(SITE_TITLE)})</author>
       <guid isPermaLink="true">${link}</guid>
     </item>`;
     })
@@ -55,6 +56,16 @@ export async function GET(): Promise<Response> {
     <description>${escapeXml(SITE_DESCRIPTION)}</description>
     <language>en</language>
     <lastBuildDate>${new Date().toUTCString()}</lastBuildDate>
+    <copyright>Copyright © 2024–${new Date().getFullYear()} ${escapeXml(SITE_TITLE)}. All rights reserved.</copyright>
+    <managingEditor>${escapeXml(CONTACT_EMAIL)} (${escapeXml(SITE_TITLE)})</managingEditor>
+    <generator>Next.js + Payload CMS</generator>
+    <image>
+      <url>${escapeXml(siteUrl)}/rss-icon-144.png</url>
+      <title>${escapeXml(SITE_TITLE)}</title>
+      <link>${escapeXml(siteUrl)}</link>
+      <width>144</width>
+      <height>144</height>
+    </image>
     <atom:link href="${escapeXml(siteUrl)}/feed.xml" rel="self" type="application/rss+xml" />${items}
   </channel>
 </rss>`;

src/app/feed.xml/route.ts

@@ -0,0 +1,46 @@
+import { PATTERNS } from "@/data/agentic-design-patterns";
+import { getPublishedPosts } from "@/lib/queries/posts";
+import { siteUrl } from "@/lib/site-config";
+
+export async function GET(): Promise<Response> {
+  const patterns = PATTERNS.filter((p) => !p.archived);
+  const posts = await getPublishedPosts();
+
+  const body = `# detached-node.dev — Full Content Index
+
+Generated: ${new Date().toISOString()}
+
+## Agentic Design Patterns (${patterns.length})
+
+${patterns
+    .map(
+      (p) =>
+        `- [${p.name}](${siteUrl}/agentic-design-patterns/${p.slug}) — ${p.oneLineSummary}`,
+    )
+    .join("\n")}
+
+## Posts (${posts.length})
+
+${posts
+    .map(
+      (p) =>
+        `- [${p.title}](${siteUrl}/posts/${p.slug})${p.summary ? ` — ${p.summary}` : ""}`,
+    )
+    .join("\n")}
+
+## Static pages
+
+- [Home](${siteUrl}/)
+- [About](${siteUrl}/about)
+- [Patterns hub](${siteUrl}/agentic-design-patterns)
+- [Patterns changelog](${siteUrl}/agentic-design-patterns/changelog)
+- [Posts hub](${siteUrl}/posts)
+`;
+
+  return new Response(body, {
+    headers: {
+      "Content-Type": "text/plain; charset=utf-8",
+      "Cache-Control": "s-maxage=3600, stale-while-revalidate=86400",
+    },
+  });
+}

src/app/llms-full.txt/route.ts

@@ -11,7 +11,7 @@ export { siteUrl } from './site-url'
 export const siteName = "detached-node";
 
 export const siteDescription =
-  "A tech blog and reference catalog on agentic AI.";
+  "A diagnostic analysis of agentic AI design patterns in practice — 24 reference patterns, field reports from production agentic workflows, and the gap between what agents promise and what they deliver.";
 
 export const siteAuthor = "detached-node";