feat: select group children on click (#9149)

## Summary

Add a setting to select all children (nodes, reroutes, nested groups)
when clicking a group on the canvas.

## Changes

- **What**: New `LiteGraph.Group.SelectChildrenOnClick` boolean setting
(default: `false`). When enabled, selecting a group cascades `select()`
to all its `_children`, and deselecting cascades `deselect()`. Recursion
handles nested groups naturally. No double-move risk — the drag handler
already uses `skipChildren=true`. The setting is wired via `onChange` to
`canvas.groupSelectChildren`, keeping litegraph free of platform
imports.

## Review Focus

- The select/deselect cascading in `LGraphCanvas.select()` /
`deselect()` — verify no infinite recursion risk with deeply nested
groups.
- The `groupSelectChildren` property is set via the setting's `onChange`
callback on `LGraphCanvas.active_canvas` — confirm this covers canvas
re-creation scenarios.

## Screenshots (if applicable)

N/A — behavioral change behind a setting toggle.

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-9149-feat-select-group-children-on-click-3116d73d365081a1a7b8c82dea95b242)
by [Unito](https://www.unito.io)

---------

Co-authored-by: GitHub Action <action@github.com>

src/platform/settings/composables/useLitegraphSettings.ts

@@ -162,4 +162,12 @@ export const useLitegraphSettings = () => {
       'Comfy.EnableWorkflowViewRestore'
     )
   })
+
+  watchEffect(() => {
+    const selectChildren = settingStore.get(
+      'LiteGraph.Group.SelectChildrenOnClick'
+    )
+    if (canvasStore.canvas)
+      canvasStore.canvas.groupSelectChildren = selectChildren
+  })
 }

src/platform/settings/constants/coreSettings.ts

@@ -1258,5 +1258,15 @@ export const CORE_SETTINGS: SettingParams[] = [
     defaultValue: true,
     experimental: true,
     versionAdded: '1.40.0'
+  },
+  {
+    id: 'LiteGraph.Group.SelectChildrenOnClick',
+    category: ['LiteGraph', 'Group', 'SelectChildrenOnClick'],
+    name: 'Select group children on click',
+    tooltip:
+      'When enabled, clicking a group selects all nodes and items inside it',
+    type: 'boolean',
+    defaultValue: false,
+    versionAdded: '1.42.0'
   }
 ]