chore: import upstream snapshot with attribution

TestsLinux/CostUsageScanExecutorLinuxTests.swift

@@ -0,0 +1,29 @@
+import CodexBarCore
+import Foundation
+import Testing
+
+@Suite
+struct CostUsageScanExecutorLinuxTests {
+    @Test
+    func returnsWorkValue() async throws {
+        let value = try await CostUsageScanExecutor.run { _ in 42 }
+        #expect(value == 42)
+    }
+
+    @Test
+    func cancelledTaskThrowsCancellationError() async {
+        let task = Task {
+            try await CostUsageScanExecutor.run { checkCancellation in
+                while true {
+                    try checkCancellation()
+                    Thread.sleep(forTimeInterval: 0.005)
+                }
+            }
+        }
+        task.cancel()
+
+        await #expect(throws: CancellationError.self) {
+            try await task.value
+        }
+    }
+}