fix: harden task recovery and DR contract handling

tests/test_tooling.py

@@ -0,0 +1,25 @@
+import importlib.util
+from pathlib import Path
+import unittest
+from unittest.mock import patch
+
+ROOT=Path(__file__).resolve().parents[1]
+spec=importlib.util.spec_from_file_location('coverage_report',ROOT/'tools/coverage_report.py')
+coverage=importlib.util.module_from_spec(spec)
+spec.loader.exec_module(coverage)
+
+
+class CoverageCompatibilityTest(unittest.TestCase):
+    def test_non_source_line_markers_do_not_enter_coverage_counts(self):
+        # Python 3.14 trace may expose None for artificial bytecode positions.
+        with patch.object(coverage.trace,'_find_executable_linenos',return_value={None:1,0:1,1:1,7:1}):
+            actual=coverage.executable_lines('example.py')
+        self.assertEqual(actual,{1,7})
+
+    def test_real_source_lines_remain_available(self):
+        lines=coverage.executable_lines(__file__)
+        self.assertTrue(lines)
+        self.assertTrue(all(type(line) is int and line>0 for line in lines))
+
+
+if __name__=='__main__':unittest.main()