fix(runtime): derive unattributed cost from usage status

tests/unit/run-usage-status.test.ts

@@ -3,6 +3,7 @@ import {
   classifyRunUsage,
   deriveLegacyRunUsageStatus,
   hasAttributableAssistantUsage,
+  isUsageStatusUnattributed,
 } from "../../src/main/run-usage-status";
 
 describe("run usage status", () => {
@@ -81,4 +82,11 @@ describe("run usage status", () => {
     );
     expect(deriveLegacyRunUsageStatus({ runStatus: "failed", unattributedCost: true })).toBe("pre_first_message");
   });
+
+  it("derives the legacy unattributed-cost flag from usage status", () => {
+    expect(isUsageStatusUnattributed("ok")).toBe(false);
+    expect(isUsageStatusUnattributed("pre_first_message")).toBe(true);
+    expect(isUsageStatusUnattributed("error_stop")).toBe(true);
+    expect(isUsageStatusUnattributed("aborted_before_usage")).toBe(true);
+  });
 });