Fix edge cases and consistency issues

pixstrip-core/tests/executor_tests.rs

@@ -112,9 +112,14 @@ fn execute_with_cancellation() {
     let executor = PipelineExecutor::with_cancel(cancel);
     let result = executor.execute(&job, |_| {}).unwrap();
 
-    // With immediate cancellation, fewer images should be processed
-    assert!(result.succeeded + result.failed <= 2);
-    assert!(result.cancelled);
+    // Cancellation flag should be set
+    assert!(result.cancelled, "result.cancelled should be true when cancel flag is set");
+    // Total processed should be less than total sources (at least some skipped)
+    assert!(
+        result.succeeded + result.failed <= 2,
+        "processed count ({}) should not exceed total (2)",
+        result.succeeded + result.failed
+    );
 }
 
 #[test]