chore: reset version to 4.2.0 for semantic-release sync

Reset manual version bump to let semantic-release handle versioning going forward.
This aligns with the last semantic-release version (4.2.0) and allows proper
automated releases based on conventional commits.

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

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

tools/installer/package.json

@@ -1,6 +1,6 @@
 {
   "name": "bmad-method",
-  "version": "4.2.1",
+  "version": "4.2.0",
   "description": "BMAD Method installer - AI-powered Agile development framework",
   "main": "lib/installer.js",
   "bin": {