docs: Add /release-docs command, changelog page, and build instructions

- Add /release-docs command for regenerating documentation site
- Add commands/README.md with usage instructions for all commands
- Add changelog.html page rendering CHANGELOG.md in HTML format
- Add changelog CSS styles to docs.css
- Update navigation in all docs pages to include changelog link
- Fix command count from 16 to 13 in navigation
- Update CLAUDE.md with:
  - Documentation Site section explaining structure
  - /release-docs command in update checklist
  - Instructions for keeping docs up-to-date

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

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

plugins/compounding-engineering/docs/pages/getting-started.html

@@ -58,6 +58,7 @@
             <li><a href="commands.html">Command Reference</a></li>
             <li><a href="skills.html">Skill Reference</a></li>
             <li><a href="mcp-servers.html">MCP Servers</a></li>
+            <li><a href="changelog.html">Changelog</a></li>
           </ul>
         </div>
       </nav>