fix(frontend): reset live log follow state on resume

frontend/src/shell/CentralStatus.test.tsx

@@ -83,3 +83,41 @@ test("preserves manual live-log scroll position away from the bottom", () => {
 
   expect(log.scrollTop).toBe(100);
 });
+
+test("resets bottom-follow when the live log resumes after becoming inactive", () => {
+  useSessionStore.setState({ transcript: [{ role: "assistant", text: "First" }] });
+  const { rerender } = render(<CentralStatus working />);
+  const log = screen.getByRole("log", { name: "Live model activity" });
+  setScrollGeometry(log, { scrollHeight: 400, clientHeight: 100, scrollTop: 100 });
+  fireEvent.scroll(log);
+
+  rerender(<CentralStatus working={false} />);
+  expect(screen.queryByRole("log", { name: "Live model activity" })).not.toBeInTheDocument();
+
+  const scrollProperties = ["scrollHeight", "clientHeight", "scrollTop"] as const;
+  const originalDescriptors = scrollProperties.map((property) =>
+    Object.getOwnPropertyDescriptor(HTMLElement.prototype, property),
+  );
+  Object.defineProperties(HTMLElement.prototype, {
+    scrollHeight: { configurable: true, value: 400 },
+    clientHeight: { configurable: true, value: 100 },
+    scrollTop: { configurable: true, writable: true, value: 0 },
+  });
+
+  try {
+    rerender(<CentralStatus working />);
+    const resumedLog = screen.getByRole("log", { name: "Live model activity" });
+    expect(resumedLog.scrollTop).toBe(400);
+
+    Object.defineProperty(resumedLog, "scrollHeight", { configurable: true, value: 500 });
+    act(() => useSessionStore.getState().applyEvent({ type: "text_delta", text: " second" }));
+
+    expect(resumedLog.scrollTop).toBe(500);
+  } finally {
+    scrollProperties.forEach((property, index) => {
+      const descriptor = originalDescriptors[index];
+      if (descriptor) Object.defineProperty(HTMLElement.prototype, property, descriptor);
+      else Reflect.deleteProperty(HTMLElement.prototype, property);
+    });
+  }
+});

frontend/src/shell/CentralStatus.tsx

@@ -21,9 +21,13 @@ export function CentralStatus({ working }: { working: boolean }) {
   const followRef = useRef(true);
 
   useLayoutEffect(() => {
+    if (!working) {
+      followRef.current = true;
+      return;
+    }
     const viewport = scrollRef.current;
     if (viewport && followRef.current) viewport.scrollTop = viewport.scrollHeight;
-  }, [rowCount, tail]);
+  }, [working, rowCount, tail]);
 
   if (!working || rows.length === 0) return null;