blog: honor canonical_url so guest posts point at their source (#151)

* blog: honor canonical_url so guest posts point at their source

A post syndicated from another blog carries the original URL in
blog_posts.canonical_url (the autoblog webhook already stores it). The post
page ignored it and always self-canonicalized, so a guest post would
compete with its source for the same words. Now the page selects
canonical_url and author, sets rel=canonical to the original when present
(self otherwise), points JSON-LD mainEntityOfPage at it, and shows readers
an "Originally published on <host>" line with the author byline.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01MxNif5tsYq4LczgG7aE8Jp

* blog: author is jsonb, render a name not [object Object]

The blog_posts.author column is jsonb (e.g. { name, url }), not text.
Extract a display name for the byline and JSON-LD instead of rendering the
object directly.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01MxNif5tsYq4LczgG7aE8Jp

---------

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

apps/logicsrc-web/src/app/blog/[slug]/page.tsx

@@ -17,8 +17,22 @@ type PostRow = {
   featured_image: { url?: string } | null;
   published_at: string;
   updated_at: string;
+  // A guest post syndicated from another blog carries the original URL here.
+  // When set, it is the canonical for search engines and is shown to readers,
+  // so a cross-post never competes with its source for the same words.
+  canonical_url: string | null;
+  // Stored as jsonb: an object like { name, url }, or occasionally a bare
+  // string. Never rendered directly, or an object prints as [object Object].
+  author: { name?: string; url?: string } | string | null;
 };
 
+/** A display name from the jsonb author, whatever shape it took. */
+function authorName(author: PostRow["author"]): string {
+  if (!author) return "";
+  if (typeof author === "string") return author;
+  return typeof author.name === "string" ? author.name : "";
+}
+
 const SITE_URL = (process.env.PUBLIC_URL ?? "https://logicsrc.com").replace(/\/$/, "");
 
 async function loadPost(slug: string): Promise<PostRow | null> {
@@ -26,7 +40,7 @@ async function loadPost(slug: string): Promise<PostRow | null> {
     const supabase = publicClient();
     const { data } = await supabase
       .from("blog_posts")
-      .select("slug, title, excerpt, html, featured_image, published_at, updated_at")
+      .select("slug, title, excerpt, html, featured_image, published_at, updated_at, canonical_url, author")
       .eq("slug", slug)
       .eq("status", "published")
       .maybeSingle();
@@ -47,7 +61,9 @@ export async function generateMetadata({
   return {
     title: `${post.title} · LogicSRC`,
     description: post.excerpt ?? undefined,
-    alternates: { canonical: `/blog/${post.slug}` },
+    // A guest post points its canonical at the original; an original post is
+    // canonical to itself.
+    alternates: { canonical: post.canonical_url ?? `/blog/${post.slug}` },
     openGraph: {
       title: post.title,
       description: post.excerpt ?? undefined,
@@ -74,6 +90,7 @@ export default async function BlogPostPage({
   const post = await loadPost(slug);
   if (!post) notFound();
 
+  const canonical = post.canonical_url ?? `${SITE_URL}/blog/${post.slug}`;
   const jsonLd = {
     "@context": "https://schema.org",
     "@type": "BlogPosting",
@@ -83,9 +100,20 @@ export default async function BlogPostPage({
     datePublished: post.published_at,
     dateModified: post.updated_at,
     url: `${SITE_URL}/blog/${post.slug}`,
-    mainEntityOfPage: `${SITE_URL}/blog/${post.slug}`,
+    // For a guest post this is the original; search engines follow it.
+    mainEntityOfPage: canonical,
+    ...(authorName(post.author) ? { author: { "@type": "Person", name: authorName(post.author) } } : {}),
     publisher: { "@id": `${SITE_URL}/#organization` },
   };
+  const byline = authorName(post.author);
+  let originHost = "";
+  if (post.canonical_url) {
+    try {
+      originHost = new URL(post.canonical_url).host;
+    } catch {
+      originHost = "";
+    }
+  }
   const html = sanitizeRenderedHtml(post.html);
 
   return (
@@ -105,6 +133,15 @@ export default async function BlogPostPage({
         </h1>
         <div style={{ color: "#5b6b7a", fontSize: "0.85rem", marginBottom: "2rem" }}>
           {formatDate(post.published_at)}
+          {byline ? ` · ${byline}` : ""}
+          {post.canonical_url ? (
+            <>
+              {" · "}
+              <a href={post.canonical_url} rel="noreferrer" style={{ color: "#5b6b7a" }}>
+                Originally published{originHost ? ` on ${originHost}` : ""}
+              </a>
+            </>
+          ) : null}
         </div>
         {post.featured_image?.url ? (
           // eslint-disable-next-line @next/next/no-img-element