fix(collab): fix corporate SSE fallback, realtime lock propagation and prevent stale overwrite

frontend/src/features/workspace/OutlinerBlock.tsx

@@ -314,6 +314,7 @@ export const OutlinerBlock: React.FC<OutlinerBlockProps> = ({
   };
 
   const handleFocus = (e: React.FocusEvent<HTMLTextAreaElement>) => {
+    if (isLockedByOther) return;
     isFocusedRef.current = true;
     onFocusBlockRef.current(block.id);
     sendCursorMovedRef.current?.(block.id, e.target.selectionStart, e.target.selectionEnd);
@@ -321,6 +322,7 @@ export const OutlinerBlock: React.FC<OutlinerBlockProps> = ({
 
   const handleBlur = () => {
     isFocusedRef.current = false;
+    if (isLockedByOther) return;
     if (debounceTimerRef.current !== null) {
       window.clearTimeout(debounceTimerRef.current);
       debounceTimerRef.current = null;