feat(workspace): split bulletpoint paragraph at cursor position on Enter

frontend/src/features/workspace/OutlinerTree.tsx

@@ -196,7 +196,7 @@ export const OutlinerTree = forwardRef<OutlinerTreeHandle, OutlinerTreeProps>(({
   }, [blocks, levelOffset]);
 
   const handleCreateBlockBelow = useCallback(
-    (afterBlockId: string, _currentContent: string) => {
+    (afterBlockId: string, newContent: string = '') => {
       if (!canEdit) return;
       const idx = blocks.findIndex((b) => b.id === afterBlockId);
       const currentBlock = idx >= 0 ? blocks[idx] : null;
@@ -207,7 +207,7 @@ export const OutlinerTree = forwardRef<OutlinerTreeHandle, OutlinerTreeProps>(({
         id: `blk_${Date.now().toString(36)}_${Math.random().toString(36).slice(2, 7)}`,
         documentId: docId,
         type: inheritedType,
-        content: '',
+        content: newContent,
         level,
         checked: false,
         collapsed: false,
@@ -464,7 +464,7 @@ export const OutlinerTree = forwardRef<OutlinerTreeHandle, OutlinerTreeProps>(({
             } else {
               const lastBlock = blocks[blocks.length - 1];
               if (lastBlock.content && lastBlock.content.trim() !== '') {
-                handleCreateBlockBelow(lastBlock.id, lastBlock.content);
+                handleCreateBlockBelow(lastBlock.id, '');
               } else {
                 focusBlockInput(lastBlock.id, 'end');
               }