Add __del__ method to MMIndexedTar for proper resource cleanup

Added a __del__ method to the MMIndexedTar class to ensure memory-mapped files
and file streams are properly closed when instances are garbage collected.
This prevents potential resource leaks when clients don't explicitly call close().
The implementation includes error handling for partially initialized objects or
already closed resources.

🤖 Generated with [Claude Code](https://claude.ai/code)

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

Author: tmbnv

src/wids/wids_mmtar.py

@@ -64,6 +64,14 @@ def close(self, dispose=False):
             self.cleanup_callback(self.fname, self.stream.fileno(), "end")
         self.mmapped_file.close()
         self.stream.close()
+        
+    def __del__(self):
+        """Ensure resources are properly closed when the object is garbage collected."""
+        try:
+            self.close()
+        except (AttributeError, ValueError, IOError):
+            # Object might be partially initialized or already closed
+            pass
 
     def _build_index(self):
         self.by_name = {}