fix(vscode): add mind-elixir dependency for webview build

The webview imports mind-elixir directly but it was only declared in
@minddoc/core. pnpm strict isolation prevents accessing undeclared deps.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Author: CoderJackZhu

packages/vscode/package.json

@@ -206,5 +206,8 @@
     "html-to-image": "^1.11.13",
     "preact": "^10.19",
     "typescript": "^5.4"
+  },
+  "dependencies": {
+    "mind-elixir": "^4.6.2"
   }
 }