chore(aio): align terminal-hydration test with single chain fetch

Main's #3744 (avoid redundant terminal history fetches) made a terminal
resume-chain hydration issue one whole-chain fetch instead of an
ancestor+current pair, so the expected call count after the terminal
watch drops from 4 to 3. The regression the test pins is unchanged: the
terminal hydration must start its own fetch rather than dedupe onto the
in-flight resume-chain hydration (count would stay 2 if mode-keying
broke).

Generated-By: PostHog Code
Task-Id: 0c511836-2180-455a-9b58-45df2a0661ec

Author: tatoalo

packages/ui/src/features/sessions/sessionServiceHost.test.ts

@@ -1919,12 +1919,12 @@ describe("SessionService", () => {
         { resume_from_run_id: "previous-run" },
       );
 
-      // The terminal hydration issues its own ancestor+current pair instead
-      // of being deduped onto the in-flight resume-chain hydration.
+      // The terminal hydration issues its own single terminal-chain fetch
+      // instead of being deduped onto the in-flight resume-chain hydration.
       await vi.waitFor(() => {
         expect(
           mockAuthenticatedClient.getTaskRunSessionLogsResult,
-        ).toHaveBeenCalledTimes(4);
+        ).toHaveBeenCalledTimes(3);
       });
       resolveFirstHydration({ entries: [], complete: true });
     });