fix(workspace): Enter keeps an empty bullet on its level when siblings follow

Outdenting an empty bullet on Enter only happens when no bullet on the
same level follows in the branch; otherwise a new bullet is added below.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

frontend/src/features/workspace/OutlinerBlock.tsx

@@ -106,6 +106,8 @@ export interface OutlinerBlockProps {
   onPasteMultiLines?: (blockId: string, textBefore: string, textAfter: string, rawLines: string[]) => void;
   /** Number or letter of a numbered-list item ("1.", "b.", "iii.") */
   listMarker?: string;
+  /** Another bullet on the same level follows: Enter in this empty bullet adds a bullet instead of outdenting */
+  siblingFollows?: boolean;
   lockedBy?: string; // someone else is editing this block
   canAppendBelow?: boolean; // the user may edit the note, so Enter in a locked block still adds one below
   onResolveConflict?: (blockId: string, accept: boolean) => void;
@@ -155,6 +157,7 @@ export const OutlinerBlock: React.FC<OutlinerBlockProps> = ({
   registerTextareaRef,
   onPasteMultiLines,
   listMarker,
+  siblingFollows = false,
   lockedBy,
   canAppendBelow,
   onResolveConflict,
@@ -961,13 +964,13 @@ export const OutlinerBlock: React.FC<OutlinerBlockProps> = ({
 
       const minLevel = levelOffset || 0;
       if (localContent === '') {
-        if (Math.max(0, block.level || 0) > minLevel) {
+        if (Math.max(0, block.level || 0) > minLevel && !siblingFollows) {
           flushDebounce(localContent);
           onIndentBlockRef.current(block.id, -1);
           return;
         }
-        // Enter in an empty numbered item at the top ends the list
-        if (block.type === 'numbered') {
+        // Enter in an empty last numbered item at the top ends the list
+        if (block.type === 'numbered' && !siblingFollows) {
           flushDebounce('', { type: 'text' });
           return;
         }

frontend/src/features/workspace/OutlinerTree.tsx

@@ -244,6 +244,21 @@ export const OutlinerTree = forwardRef<OutlinerTreeHandle, OutlinerTreeProps>(({
 
   const listLabels = useMemo(() => numberedLabels(blocks), [blocks]);
 
+  // Whether another bullet on the same level follows (before the branch ends); an empty bullet
+  // is then not outdented by Enter
+  const siblingFollows = useCallback(
+    (index: number) => {
+      const level = blocks[index]?.level || 0;
+      for (let i = index + 1; i < blocks.length; i++) {
+        const l = blocks[i].level || 0;
+        if (l < level) return false;
+        if (l === level) return true;
+      }
+      return false;
+    },
+    [blocks]
+  );
+
   const handleCreateBlockBelow = useCallback(
     (afterBlockId: string, newContent: string = '') => {
       if (!canEdit) return;
@@ -617,6 +632,7 @@ export const OutlinerTree = forwardRef<OutlinerTreeHandle, OutlinerTreeProps>(({
             block={block}
             index={index}
             isLast={isLast}
+            siblingFollows={siblingFollows(index)}
             maxAllowedLevel={maxAllowedLevel}
             hasChildren={hasChildren}
             isFocused={focusedBlockId === block.id}

frontend/src/features/workspace/__tests__/OutlinerBlock.caret.test.tsx

@@ -207,6 +207,33 @@ describe('slash command menu and outliner fixes', () => {
     expect(onCreateBelow).toHaveBeenCalledWith('b1', '');
   });
 
+  it('keeps an empty indented bullet on its level when another bullet on that level follows', () => {
+    const onIndent = vi.fn();
+    const onCreateBelow = vi.fn();
+    const { container } = render(
+      <OutlinerBlock
+        docId="d"
+        block={{ id: 'b1', type: 'bullet', content: '', level: 1 } as DocumentBlock}
+        index={0}
+        isLast={false}
+        siblingFollows
+        maxAllowedLevel={2}
+        hasChildren={false}
+        isFocused
+        canEdit
+        onUpdateBlock={() => {}}
+        onCreateBlockBelow={onCreateBelow}
+        onDeleteBlock={() => {}}
+        onIndentBlock={onIndent}
+        onNavigateFocus={() => {}}
+        registerTextareaRef={() => {}}
+      />
+    );
+    fireEvent.keyDown(container.querySelector('textarea') as HTMLTextAreaElement, { key: 'Enter' });
+    expect(onIndent).not.toHaveBeenCalled();
+    expect(onCreateBelow).toHaveBeenCalledWith('b1', '');
+  });
+
   it('inserts a bare URL for /link with a web address in an empty bullet, and [Text](url) otherwise', () => {
     const updates: DocumentBlock[] = [];
     const block = { id: 'b1', type: 'bullet', content: '', level: 0 } as DocumentBlock;