feat: add MCP server package for npx distribution (#284)

* feat: add MCP server package for npx distribution

- Self-contained MCP server with embedded HTTP server
- Real-time browser preview via draw.io iframe
- Tools: start_session, display_diagram, edit_diagram, get_diagram, export_diagram
- Port retry limit (6002-6020) and session TTL cleanup (1 hour)
- Published as @next-ai-drawio/mcp-server on npm

* chore: bump version to 0.1.2

* docs: add MCP server section to README (preview feature)

* docs: add multi-client installation instructions for MCP server

* fix: exclude packages from Next.js build

* docs: use @latest instead of -y flag for npx (match Playwright MCP style)

* chore: bump version to 0.4.3 and add release notes

* chore: remove release notes

* feat: add MCP server notice to example panel

.gitignore

@@ -2,6 +2,8 @@
 
 # dependencies
 /node_modules
+packages/*/node_modules
+packages/*/dist
 /.pnp
 .pnp.*
 .yarn/*
@@ -47,3 +49,4 @@ push-via-ec2.sh
 .open-next/
 .wrangler/
 .env*.local
+