chore: Change domain to www.gravitykit.dev

Update site URL, CNAME, and robots.txt to use www subdomain.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: zackkatz

docusaurus.config.js

@@ -43,7 +43,7 @@ const config = {
   favicon: 'img/favicon-192.png',
 
   // Set the production url of your site here
-  url: 'https://gravitykit.dev',
+  url: 'https://www.gravitykit.dev',
   // Set the /<baseUrl>/ pathname under which your site is served
   baseUrl: '/',
 

static/CNAME

@@ -1 +1 @@
-gravitykit.dev
+www.gravitykit.dev

static/robots.txt

@@ -1,11 +1,11 @@
 # Robots.txt for GravityKit Developer Documentation
-# https://gravitykit.dev
+# https://www.gravitykit.dev
 
 User-agent: *
 Allow: /
 
 # Sitemap location
-Sitemap: https://gravitykit.dev/sitemap.xml
+Sitemap: https://www.gravitykit.dev/sitemap.xml
 
 # Disallow build artifacts and internal paths
 Disallow: /assets/js/*.js.map