feat(FN-5103): surface landed-files attribution flags in task changes UI

Fusion-Task-Id: FN-5103
Fusion-Task-Lineage: e4e4d9ba-4884-4feb-b18b-a30e799c3fb1

packages/dashboard/app/components/TaskChangesTab.tsx

@@ -372,6 +372,12 @@ export function TaskChangesTab({ taskId, worktree, projectId, column, mergeDetai
               Merged {new Date(mergeDetails.mergedAt).toLocaleString()}
             </div>
           )}
+          {mergeDetails.noOpVerifiedShortCircuit && (
+            <div className="text-muted">Verified short-circuit — work was already on main (rebase walked foreign commits).</div>
+          )}
+          {mergeDetails.landedFilesCaptureFallback === "attribution-failed" && (
+            <div className="text-muted">Landed-files set may include foreign commits (attribution unavailable).</div>
+          )}
         </div>
       )}
 

packages/dashboard/app/components/__tests__/TaskChangesTab.test.tsx

@@ -316,6 +316,30 @@ describe("TaskChangesTab — commit-backed (done tasks)", () => {
     expect(screen.getByText(/Merged .+/)).toBeTruthy();
   });
 
+  it("renders attribution notes for short-circuit and fallback merge details", async () => {
+    mockFetchTaskDiff.mockResolvedValue(DONE_TASK_DIFF);
+
+    render(
+      <TaskChangesTab
+        taskId="FN-001"
+        worktree={undefined}
+        column="done"
+        mergeDetails={{
+          ...MERGE_DETAILS,
+          noOpVerifiedShortCircuit: true,
+          landedFilesCaptureFallback: "attribution-failed",
+        }}
+      />,
+    );
+
+    await waitFor(() => {
+      expect(screen.getByText("Verified short-circuit — work was already on main (rebase walked foreign commits)."))
+        .toBeTruthy();
+    });
+    expect(screen.getByText("Landed-files set may include foreign commits (attribution unavailable)."))
+      .toBeTruthy();
+  });
+
   it("uses mergeDetails stats for summary", async () => {
     mockFetchTaskDiff.mockResolvedValue(DONE_TASK_DIFF);