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

package-lock.json

@@ -1,12 +1,12 @@
 {
   "name": "markdown-converter",
-  "version": "4.4.1",
+  "version": "4.4.4",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "markdown-converter",
-      "version": "4.4.1",
+      "version": "4.4.4",
       "license": "MIT",
       "dependencies": {
         "@codemirror/autocomplete": "^6.20.1",