feat: add scroll-to-top button and improve pagination handling

- Implemented a scroll-to-top button in the viewer UI for better navigation.
- Added styles for the scroll-to-top button in viewer.html and viewer-template.html.
- Created a new ScrollToTop component to manage visibility and scrolling behavior.
- Updated Feed component to include the ScrollToTop component.
- Enhanced pagination logic in usePagination hook to prevent stale closures and improve performance.
- Modified SDKAgent to include additional observation fields for better data handling.

src/ui/viewer/App.tsx

@@ -72,12 +72,13 @@ export function App() {
     } catch (error) {
       console.error('Failed to load more data:', error);
     }
-  }, [pagination]);
+  }, [pagination.observations, pagination.summaries, pagination.prompts]);
 
-  // Load first page when filter changes or pagination handlers update
+  // Load first page only when filter changes
   useEffect(() => {
     handleLoadMore();
-  }, [currentFilter, handleLoadMore]);
+    // eslint-disable-next-line react-hooks/exhaustive-deps
+  }, [currentFilter]); // Only re-run when filter changes, not when handleLoadMore changes
 
   return (
     <div className="container">