refactor: normalize data directory naming, and consolidate serial connection handling

src/pygui/backend/data/file_browser.py

@@ -10,6 +10,7 @@ from PySide6.QtWidgets import QFileDialog, QMessageBox
 
 from pygui.backend.data.csv_file_metadata import CSVFileMetadata
 from pygui.backend.wafer.zwafer_parser import ZWaferParser
+from pygui.backend.data.constants import DEFAULT_DATA_DIR_NAME
 
 
 # ===== File Browser Model =====
@@ -232,7 +233,7 @@ class FileBrowser(QObject):
             QStandardPaths.DocumentsLocation
         )
         base_dir = Path(documents_dir) if documents_dir else (Path.home() / "Documents")
-        return base_dir / "ISC_DATA"
+        return base_dir / DEFAULT_DATA_DIR_NAME
 
     def _set_current_directory(self, directory: Path) -> None:
         normalized = Path(directory)