Give each route its own title and canonical, and add robots.txt plus a sitemap.

The root layout was stamping the homepage title and production root onto every page. Routes now supply a page segment through one em-dash template, canonicals follow the request path, and non-production hosts disallow crawlers.

Co-authored-by: Cursor <cursoragent@cursor.com>

lib/publicSitemap.ts

@@ -0,0 +1,42 @@
+import type { MetadataRoute } from "next";
+import { getAllBlogPosts } from "./content";
+import { sitemapUrl } from "./siteMetadata";
+import { USE_CASE_DETAIL_SLUGS } from "./useCaseSyntheticPost";
+
+const STATIC_PUBLIC_PATHS = [
+  "/",
+  "/about",
+  "/learn",
+  "/templates",
+  "/blog",
+  "/use-cases",
+  "/how-it-works",
+  "/privacy",
+  "/terms",
+  "/cookies",
+] as const;
+
+/**
+ * Public marketing URLs for `/sitemap.xml`. Omits signed-in product routes
+ * (`/create`, `/login`, `/profile`), admin, and `/rules/[id]` (those ids are
+ * not known without the database).
+ */
+export function buildPublicSitemap(): MetadataRoute.Sitemap {
+  const entries: MetadataRoute.Sitemap = STATIC_PUBLIC_PATHS.map((path) => ({
+    url: sitemapUrl(path),
+  }));
+
+  for (const post of getAllBlogPosts()) {
+    entries.push({
+      url: sitemapUrl(`/blog/${post.slug}`),
+      lastModified: post.lastModified,
+    });
+  }
+
+  for (const slug of USE_CASE_DETAIL_SLUGS) {
+    entries.push({ url: sitemapUrl(`/use-cases/${slug}`) });
+    entries.push({ url: sitemapUrl(`/use-cases/${slug}/rule`) });
+  }
+
+  return entries;
+}