fix: resolve flaky test in test_issue_152_153_edge_cases.py

Fix TestVariantDetectionEdgeCases::test_is_exploded_directory_edge_cases
that was failing due to temporary directory conflicts.

## Issue
- Test was creating directories in /tmp which could conflict
  between test runs (FileExistsError: /tmp/empty already exists)

## Solution
- Move all test directories into the tempfile.TemporaryDirectory context
- Use unique subdirectory names within the temp directory
- Ensure proper cleanup and isolation between test runs

## Verification
✅ Test now passes consistently across multiple runs
✅ All 14 edge case tests pass (100% success rate)
✅ All 40 manifest/detection tests still pass
✅ No test isolation issues

The edge case tests now provide robust validation of manifest
and detection systems without flaky failures.

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

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

tests/test_issue_152_153_edge_cases.py

@@ -311,11 +311,13 @@ class TestVariantDetectionEdgeCases:
             temp_path = Path(temp_dir)
 
             # Test with just manifest.md
-            (temp_path / "manifest.md").touch()
-            assert detector.is_exploded_directory(temp_path) is True
+            manifest_test_dir = temp_path / "manifest_test"
+            manifest_test_dir.mkdir()
+            (manifest_test_dir / "manifest.md").touch()
+            assert detector.is_exploded_directory(manifest_test_dir) is True
 
             # Test with .mdd extension directory with exploded structure
-            mdd_dir = temp_path.parent / f"test_{hash(temp_path)}.mdd"
+            mdd_dir = temp_path / "test_structure.mdd"
             mdd_dir.mkdir()
             # Create exploded structure with numbered directories
             (mdd_dir / "01_chapter").mkdir()
@@ -323,7 +325,7 @@ class TestVariantDetectionEdgeCases:
             assert detector.is_exploded_directory(mdd_dir) is True
 
             # Test with completely empty directory
-            empty_dir = temp_path.parent / "empty"
+            empty_dir = temp_path / "empty_test"
             empty_dir.mkdir()
             assert detector.is_exploded_directory(empty_dir) is False