fix: guard rAF retry in setFocusTarget with focus containment check

Skip the requestAnimationFrame retry of giveFocus() if focus has
already moved outside the block, preventing unnecessary calls when
the user has clicked elsewhere between scheduling and execution.

Signed-off-by: majiayu000 <1835304752@qq.com>

Author: majiayu000

frontend/app/block/block.tsx

@@ -241,7 +241,9 @@ const BlockFull = memo(({ nodeModel, viewModel }: FullBlockProps) => {
         focusElemRef.current?.focus({ preventScroll: true });
         pendingFocusRafRef.current = requestAnimationFrame(() => {
             pendingFocusRafRef.current = null;
-            viewModel?.giveFocus?.();
+            if (blockRef.current?.contains(document.activeElement)) {
+                viewModel?.giveFocus?.();
+            }
         });
     }, [viewModel]);