Release 0.4.0: build errors in the Problems view

- gm2 diagnostics published as clickable Problems markers
- Verified end-to-end in headless Chrome (notification + markers,
  zero console errors)

package.json

@@ -1,7 +1,7 @@
 {
   "private": true,
   "name": "modula2-ide",
-  "version": "0.3.1",
+  "version": "0.4.0",
   "description": "GNU Modula-2 IDE built on Eclipse Theia",
   "engines": {
     "node": ">=24",