chore: bump version to 4.42.0 for release

- Update main package.json to 4.42.0
- Update installer package.json to 4.42.0
- Add PR validation workflow and contribution checks
- Add pre-release and fix scripts
- Update CONTRIBUTING.md with validation requirements

package.json

@@ -1,7 +1,7 @@
 {
   "$schema": "https://json.schemastore.org/package.json",
   "name": "bmad-method",
-  "version": "4.40.1",
+  "version": "4.42.0",
   "description": "Breakthrough Method of Agile AI-driven Development",
   "keywords": [
     "agile",