chore: bump to v2.28.0 and fix repo URLs

- Bump version to 2.28.0 in plugin.json and marketplace.json
  (CHANGELOG was updated but version numbers were missed)
- Fix all repo URLs from kieranklaassen/* to EveryInc/compound-engineering-plugin
- Update component counts in docs: 28 agents, 24 commands, 15 skills, 1 MCP

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

docs/pages/getting-started.html

@@ -97,7 +97,7 @@
           <h3>Step 1: Add the Marketplace</h3>
           <p>Think of the marketplace as an app store. You're adding it to Claude Code's list of places to look for plugins:</p>
           <div class="card-code-block">
-            <pre><code>claude /plugin marketplace add https://github.com/kieranklaassen/every-marketplace</code></pre>
+            <pre><code>claude /plugin marketplace add https://github.com/EveryInc/compound-engineering-plugin</code></pre>
           </div>
 
           <h3>Step 2: Install the Plugin</h3>