style: Apply code formatting with ruff format

- Formatted core service implementation
- Formatted CLI main module
- Formatted test file with proper line breaks and indentation

All formatting, linting, and type checks now pass.

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

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

src/deltaglider/app/cli/main.py

@@ -433,7 +433,9 @@ def rm(
                         # Show warnings if any references were kept
                         for warning in result.get("warnings", []):
                             if "Kept reference" in warning:
-                                click.echo(f"Keeping reference file (still in use): s3://{bucket}/{warning.split()[2]}")
+                                click.echo(
+                                    f"Keeping reference file (still in use): s3://{bucket}/{warning.split()[2]}"
+                                )
 
                 # Report any errors
                 if result["failed_count"] > 0:

src/deltaglider/core/service.py

@@ -797,7 +797,9 @@ class DeltaService:
 
                 # Check if there are any remaining files in this deltaspace
                 # (outside of the deletion prefix)
-                deltaspace_list_prefix = f"{bucket}/{deltaspace_prefix}" if deltaspace_prefix else bucket
+                deltaspace_list_prefix = (
+                    f"{bucket}/{deltaspace_prefix}" if deltaspace_prefix else bucket
+                )
                 remaining_objects = list(self.storage.list(deltaspace_list_prefix))
 
                 # Filter out objects that are being deleted (within our deletion scope)
@@ -830,7 +832,9 @@ class DeltaService:
                     warnings_list = result["warnings"]
                     assert isinstance(warnings_list, list)
                     warnings_list.append(f"Kept reference {ref_key} (still in use)")
-                    self.logger.info(f"Kept reference {ref_key} - still in use outside deletion scope")
+                    self.logger.info(
+                        f"Kept reference {ref_key} - still in use outside deletion scope"
+                    )
 
             except Exception as e:
                 failed_count = result["failed_count"]