feat(mcp): add XML validation and auto-fix to MCP server (#336)

* feat(mcp): add XML validation and auto-fix to MCP server

- Add xml-validation.ts with validateAndFixXml function
- Integrate validation into display_diagram tool (fails if unfixable)
- Integrate validation into edit_diagram tool (auto-fix each operation)
- Fix bug: typo fixes now run before foreign tag removal
- Fix bug: use before/after comparison instead of regex .test()

* style: auto-format with Biome

* chore(mcp): bump version to 0.1.3

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Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>

packages/mcp-server/package.json

@@ -1,6 +1,6 @@
 {
     "name": "@next-ai-drawio/mcp-server",
-    "version": "0.1.2",
+    "version": "0.1.3",
     "description": "MCP server for Next AI Draw.io - AI-powered diagram generation with real-time browser preview",
     "type": "module",
     "main": "dist/index.js",