feat(workspace): bar above the phone keyboard to indent, outdent and move bullets

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

frontend/src/lib/outlineList.ts

@@ -63,3 +63,30 @@ export function numberedLabels(blocks: DocumentBlock[]): Map<string, string> {
   }
   return labels;
 }
+
+// Swaps a bullet (with its children) with the previous (-1) or next (+1) bullet on the same level
+// under the same parent. Returns the same array when there is no such sibling.
+export function moveSibling<T extends Pick<DocumentBlock, 'id' | 'level'>>(blocks: T[], blockId: string, direction: -1 | 1): T[] {
+  const lvl = (b: T) => Math.max(0, b.level || 0);
+  const subtreeEnd = (start: number) => {
+    let end = start + 1;
+    while (end < blocks.length && lvl(blocks[end]) > lvl(blocks[start])) end++;
+    return end;
+  };
+  const idx = blocks.findIndex((b) => b.id === blockId);
+  if (idx === -1) return blocks;
+  const level = lvl(blocks[idx]);
+  const end = subtreeEnd(idx);
+  if (direction === -1) {
+    for (let i = idx - 1; i >= 0; i--) {
+      if (lvl(blocks[i]) < level) return blocks; // reached the parent: already the first child
+      if (lvl(blocks[i]) === level) {
+        return [...blocks.slice(0, i), ...blocks.slice(idx, end), ...blocks.slice(i, idx), ...blocks.slice(end)];
+      }
+    }
+    return blocks;
+  }
+  if (end >= blocks.length || lvl(blocks[end]) !== level) return blocks; // already the last child
+  const nextEnd = subtreeEnd(end);
+  return [...blocks.slice(0, idx), ...blocks.slice(end, nextEnd), ...blocks.slice(idx, end), ...blocks.slice(nextEnd)];
+}