Bump version to 0.9.0-beta for beta testing

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: reidspencer

package.json

@@ -2,7 +2,7 @@
   "name": "riddl-vscode",
   "displayName": "RIDDL Language Support",
   "description": "Language support for RIDDL (Reactive Interface to Domain Definition Language)",
-  "version": "0.9.0",
+  "version": "0.9.0-beta",
   "publisher": "ossuminc",
   "license": "Apache-2.0",
   "icon": "icons/riddl-icon.png",