refactor: Improve filename sanitization by removing shell variable patterns and directly stripping invalid characters.

src/utils.py

@@ -157,17 +157,20 @@ def sanitize_filename(filename: str) -> str:
     
     # Remove control characters and non-printable characters
     filename = re.sub(r'[\x00-\x1f\x7f]', '', filename)
+
+    # remove potential $( ) and ${ }
+    filename = re.sub(r'\$[\(\{].*?[\)\}]', '', filename)
     
+    # remove any remaining $( or ${
+    filename = filename.replace('$(', '').replace('${', '')
+
     # Allow alphanumeric, underscore, hyphen, space, and dots
     # Remove other potentially dangerous characters.
-    filename = re.sub(r'[^a-zA-Z0-9_\-\.\ ]', '_', filename)
+    filename = re.sub(r'[^a-zA-Z0-9_\-\.\ ]', '', filename)
     
     # Remove consecutive dots to prevent directory traversal attempts like '..'
     filename = re.sub(r'\.{2,}', '.', filename)
 
-    # remove potential $(
-    filename = re.sub(r'\$\([\s\S]*?\)', '', filename)
-
     # Ensure filename is not practically empty after sanitization
     if not filename.strip() or filename.strip().replace('.', '') == '':
          raise ValueError("Filename invalid after sanitization")