nook: fix the landing title, isolate /blog, grow the sitemap

The landing page spent its strongest on-page signal on the word "Home";
the title now carries the positioning line and the OG title carries the
full brand phrase. /blog on a product subdomain served the personal blog
in dev (vinxi ignores the vercel.json rewrites that protect production),
splitting the brand and crawl equity — subdomain hits now render the
shared 404. /agents, /changelog and /faq join the sitemap registry so
they are indexed as they land.

Tests: bun test (539 pass); vinxi build clean, no new tsc errors.

Issues: FRE-8, FRE-15, FRE-9

src/lib/sitemap-routes.ts

@@ -83,6 +83,9 @@ export const SITEMAP_ROUTES: Record<SiteId, SitemapEntry[]> = {
   nook: [
     { path: "/", changefreq: "weekly", priority: 1.0 },
     { path: "/checkout", changefreq: "monthly", priority: 0.5 },
-    { path: "/privacy", changefreq: "yearly", priority: 0.4 }
+    { path: "/privacy", changefreq: "yearly", priority: 0.4 },
+    { path: "/agents", changefreq: "weekly", priority: 0.9 },
+    { path: "/changelog", changefreq: "daily", priority: 0.7 },
+    { path: "/faq", changefreq: "monthly", priority: 0.8 }
   ]
 };