Tree: Reorder... for a component's children

Right-click a component (or the app) with two or more children to move them
up and down; OK applies the new order, which is the order they run in. On a
device the order goes there first via Sox reorder, checked against the
device's children, and the file is left alone if it is refused. Undoable.

Also: device host in editor.properties.

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

sax_file.py

@@ -483,6 +483,43 @@ def rename_component(comp_element, new_name):
     return True
 
 
+def reorder_children(parent, new_order):
+    """Gives `parent`'s child components a new order, which is the order they run in.
+
+    Returns True when the order changed. On a device the new order goes there first,
+    and the file is left alone if it does not.
+    """
+    root = app_state.xml_root_element
+    if root is None:
+        return False
+    old_order = [child for child in parent if child.tag == "comp"]
+    new_order = list(new_order)
+    if new_order == old_order:
+        return False
+    if (len(new_order) != len(old_order)
+            or {id(c) for c in new_order} != {id(c) for c in old_order}):
+        return False
+
+    name = parent.get("name", "app")
+    if app_state.live_mode:
+        if not live_hooks.live_reorder_children(parent, new_order):
+            live_hooks.warn_failure("Reorder", f"{name} was not reordered on the device")
+            return False
+
+    undo.apply_child_order(parent, new_order)
+    command_class = (undo.LiveReorderChildrenCommand if app_state.live_mode
+                     else undo.ReorderChildrenCommand)
+    undo.push(command_class(parent, old_order, new_order, label=f"reorder {name}"))
+
+    app_state.mark_dirty()
+    refresh_treeview_from_dom(root)
+    wiresheet.render_current_sheet()
+
+    where = " on the device" if app_state.live_mode else ""
+    app_state.set_status(f"{name} reordered{where}.")
+    return True
+
+
 def allocate_component_id():
     """Lowest unused id, matching how this app's ids are dense with no gaps."""
     used = set()