Fix test skip condition for scikit-learn-extra tests

Problem:
- Tests in test_intensity_label_filter.py were failing on macOS CI
- The skip condition checked if import succeeded, but not if sklearn-extra was actually available
- Functions imported successfully but raised ImportError when called

Root Cause:
- Test was checking: 'try: import functions; HAS_KMEDOIDS = True'
- But functions exist even when sklearn-extra is missing
- Functions check _HAS_KMEDOIDS internally and raise ImportError at runtime
- Result: tests run when they should be skipped

Solution:
- Import _HAS_KMEDOIDS flag directly from the module
- Use this flag for @pytest.mark.skipif decorator
- Now tests properly skip when sklearn-extra is unavailable

Testing:
- All 171 tests still pass locally (with sklearn-extra installed)
- Tests will now properly skip on CI if sklearn-extra is missing
- Eliminates spurious failures on macOS GitHub Actions

Author: macromeer

src/napari_tmidas/_tests/test_intensity_label_filter.py

@@ -4,17 +4,15 @@
 import numpy as np
 import pytest
 
-# Try importing the functions - they may not be available if sklearn-extra is not installed
-try:
-    from napari_tmidas.processing_functions.intensity_label_filter import (
-        _calculate_label_mean_intensities,
-        _cluster_intensities,
-        _filter_labels_by_threshold,
-    )
-
-    HAS_KMEDOIDS = True
-except ImportError:
-    HAS_KMEDOIDS = False
+# Import the module and check if k-medoids is available
+from napari_tmidas.processing_functions.intensity_label_filter import (
+    _HAS_KMEDOIDS,
+    _calculate_label_mean_intensities,
+    _cluster_intensities,
+    _filter_labels_by_threshold,
+)
+
+HAS_KMEDOIDS = _HAS_KMEDOIDS
 
 
 @pytest.mark.skipif(