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

---------

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

package.json

@@ -76,7 +76,7 @@
     },
     "devDependencies": {
         "@anthropic-ai/tokenizer": "^0.0.4",
-        "@biomejs/biome": "^2.3.8",
+        "@biomejs/biome": "^2.3.10",
         "@tailwindcss/postcss": "^4",
         "@tailwindcss/typography": "^0.5.19",
         "@types/negotiator": "^0.6.4",