feat: add JSONEditor Arrange dialog to reorder sections and add headings

Add an Arrange toolbar button (and SpeedDial entry) that opens a
JSONEditor seeded from the current sections. Editing the outline (drag to
reorder, add nested heading blocks) updates _story_outline, which drives
the export order.

Author: ghostiee-11

lumen/ai/report.py

@@ -977,6 +977,11 @@ def _init_view(self):
             color="default", margin=0, visible=False,
             description="Annotate the report with an AI-written story",
         )
+        self._arrange = IconButton(
+            icon="reorder", on_click=self._open_arrange_dialog, size="large",
+            color="default", margin=0, visible=False,
+            description="Arrange the report (reorder sections and add headings)",
+        )
         self._export = MenuButton(
             label="", icon="get_app", variant="text", color="default",
             margin=0, size="large", visible=False,
@@ -1011,13 +1016,24 @@ def _init_view(self):
             close_on_click=True,
             title=f"Report Settings: {self.title}",
         )
+        self._outline_editor = pn.widgets.JSONEditor(
+            mode="tree", sizing_mode="stretch_width", height=400,
+        )
+        self._outline_editor.param.watch(self._on_outline_change, "value")
+        self._outline_dialog = Dialog(
+            self._outline_editor,
+            show_close_button=True,
+            title="Arrange Report",
+            width_option="md",
+        )
         self._menu = Row(
             self._header_title,
             self._run,
             self._stop,
             self._clear,
             self._collapse,
             self._annotate,
+            self._arrange,
             self._export,
             self._settings,
             sizing_mode="stretch_width"
@@ -1028,6 +1044,7 @@ def _init_view(self):
                 {"label": "Stop Report", "icon": "stop"},
                 {"label": "Clear Report", "icon": "clear"},
                 {"label": "Annotate Report", "icon": "auto_stories"},
+                {"label": "Arrange Report", "icon": "reorder"},
                 {"label": "Export as Notebook", "icon": "description", "format": "ipynb"},
                 {"label": "Export as HTML", "icon": "language", "format": "html"},
                 {"label": "Configure Report", "icon": "settings"}
@@ -1054,6 +1071,7 @@ def _init_view(self):
         self._container = Column(
             self._view,
             self._dialog,
+            self._outline_dialog,
             margin=(0, 0, 0, 5),
             sizing_mode="stretch_both",
             height_policy='fit',
@@ -1074,6 +1092,8 @@ async def _trigger_event(self, item: dict):
             self.reset()
         elif icon == "auto_stories":
             await self._annotate_report()
+        elif icon == "reorder":
+            self._open_arrange_dialog()
         elif icon in ("description", "language"):
             fmt = item.get("format", "ipynb")
             self._export.value = {"format": fmt}
@@ -1094,6 +1114,7 @@ def _update_icon_visibility(self):
         self._collapse.visible = has_outputs
         self._annotate.visible = has_outputs
         self._annotate.disabled = self.llm is None
+        self._arrange.visible = has_outputs
         self._export.visible = has_outputs
         self._settings.visible = has_outputs
         # Only animate play button when no outputs
@@ -1212,6 +1233,14 @@ def _expand_all(self, event=None):
     def _open_settings(self, event=None):
         self._dialog.open = True
 
+    def _open_arrange_dialog(self, event=None):
+        # Seed from the current arrangement, or the default section order.
+        self._outline_editor.value = self._story_outline or self._build_default_outline()
+        self._outline_dialog.open = True
+
+    def _on_outline_change(self, event):
+        self._story_outline = event.new or []
+
     async def _annotate_report(self, event=None):
         """Write an AI story over the selected sections and insert it into the report."""
         if self.llm is None or not len(self):

lumen/tests/ai/test_story.py

@@ -219,3 +219,23 @@ async def test_report_outline_inserts_headings():
     nb = _nb_text(report)
     assert "Introduction" in nb
     assert nb.index("Introduction") < nb.index("A done")
+
+
+async def test_report_arrange_editor_seeds_and_binds_outline():
+    report = Report(
+        Section(A(order=[]), title='Section A'),
+        Section(B(order=[]), title='Section B'),
+        title='R',
+    )
+    await report.execute()
+
+    # Opening the arrange dialog seeds the editor from the current sections.
+    report._open_arrange_dialog()
+    assert report._outline_editor.value == [{"section": "Section A"}, {"section": "Section B"}]
+    assert report._outline_dialog.open is True
+
+    # Editing the JSONEditor updates the outline, which reorders the export.
+    report._outline_editor.value = [{"section": "Section B"}, {"section": "Section A"}]
+    assert report._story_outline == [{"section": "Section B"}, {"section": "Section A"}]
+    nb = _nb_text(report)
+    assert nb.index("B done") < nb.index("A done")