docs: update site title and canonical URL

Rename the Starlight site to "Rootiest Fish Config" and switch its
canonical URL from the Cloudflare Pages subdomain to
fish-config.rootiest.fyi (now aliased in Cloudflare). Updates all
references in README, config-help, open-url, and the manual, and
regenerates the concat/man-page artifacts to match.

docs/site/astro.config.mjs

@@ -3,10 +3,10 @@ import starlight from '@astrojs/starlight';
 import sidebar from './src/sidebar.json' with { type: 'json' };
 
 export default defineConfig({
-  site: 'https://fish-config-docs.pages.dev',
+  site: 'https://fish-config.rootiest.fyi',
   integrations: [
     starlight({
-      title: 'Fish Config',
+      title: 'Rootiest Fish Config',
       description: 'Reference manual for the rootiest fish configuration.',
       social: [
         {