fix(batch): resolve pandoc path handling and include-subfolders option

- Normalize pandoc command parsing with path.basename() to support bundled binary paths
- Use bundled pandoc binary in convertWithPandoc instead of relying on PATH
- Forward includeSubfolders checkbox state from renderer to main process
- Add pandoc availability check before batch conversion
- Re-enable Start button when batch conversion completes
- Clean up obsolete dist build artifact causing test snapshot warning
- Bump version to 4.4.4

src/plugins/built-in/_sample/manifest.json

@@ -5,9 +5,7 @@
   "description": "Demonstrates the plugin system. Safe to delete.",
   "icon": "puzzle",
   "extensionPoints": {
-    "commands": [
-      { "id": "hello", "label": "Sample: Hello World", "shortcut": "" }
-    ]
+    "commands": [{ "id": "hello", "label": "Sample: Hello World", "shortcut": "" }]
   },
   "settings": []
 }