test: allow zero coverage in resource sampling checks

crates/fabric-core/src/runtime.rs

@@ -5286,7 +5286,8 @@ for line in sys.stdin:
             "peak was lost after worker exit: {summary:?}"
         );
         assert!(summary.sample_count >= 3);
-        assert!(gauge.covered_fraction > 0.0);
+        // A spike sample need not have a neighbor within twice the interval.
+        assert!((0.0..=1.0).contains(&gauge.covered_fraction));
         let path = &summary.samples.as_ref().unwrap().path;
         let rows: Vec<Value> = fs::read_to_string(path)
             .unwrap()

tests/python/test_system_stats.py

@@ -85,7 +85,8 @@ async def test_sdk_returns_typed_samples_and_artifacts_without_relay_or_recordin
         sampled.resident_memory_bytes.sampled_peak
         >= sampled.resident_memory_bytes.final_value
     )
-    assert 0 < sampled.resident_memory_bytes.covered_fraction <= 1
+    # Gaps above twice the sampling interval do not contribute coverage.
+    assert 0 <= sampled.resident_memory_bytes.covered_fraction <= 1
     assert (
         RunResult.from_mapping(result.to_mapping()).system_stats == result.system_stats
     )