fix(liveview): apply collapse filter in read-only canvas

LiveView.tsx passed raw nodes/edges from the store straight to
ReactFlow, bypassing the collapse pipeline that CanvasContainer applies
in the editor. Result: a group or zone marked collapsed in edit mode
still showed all its contents on /view?key=... and in standalone live
view. The flag was being persisted and read correctly — only the
read-only canvas ignored it.

Reuse the same memoized computeCollapseInfo + rewireEdgesForCollapse
pipeline. Add two regression tests that load a /liveview payload with
a collapsed group and assert the children never reach ReactFlow.

frontend/src/utils/__tests__/group.collapse.integration.test.ts

@@ -0,0 +1,43 @@
+import { describe, it, expect } from 'vitest'
+import { renderHook, act } from '@testing-library/react'
+import { useCanvasStore } from '../../stores/canvasStore'
+import { computeCollapseInfo } from '../collapseFilter'
+import type { Node } from '@xyflow/react'
+import type { NodeData } from '@/types'
+
+const mk = (id: string, type: NodeData['type'] = 'server'): Node<NodeData> => ({
+  id,
+  type,
+  position: { x: 100, y: 100 },
+  data: { label: id, type, status: 'online', services: [] },
+})
+
+describe('integration — createGroup + toggleNodeCollapsed hides children', () => {
+  it('hides parentId children of a collapsed group container', () => {
+    const { result } = renderHook(() => useCanvasStore())
+    act(() => {
+      result.current.addNode(mk('c1'))
+      result.current.addNode(mk('c2'))
+      result.current.createGroup(['c1', 'c2'], 'My Group')
+    })
+    // Find the auto-generated group id.
+    const grp = result.current.nodes.find((n) => n.type === 'group')!
+    expect(grp).toBeDefined()
+    expect(result.current.nodes.find((n) => n.id === 'c1')!.parentId).toBe(grp.id)
+
+    // Pre-collapse: all visible.
+    let info = computeCollapseInfo(result.current.nodes)
+    expect(info.visibleIds.has('c1')).toBe(true)
+    expect(info.visibleIds.has('c2')).toBe(true)
+
+    // Collapse the group via the store action.
+    act(() => result.current.toggleNodeCollapsed(grp.id))
+    expect(result.current.nodes.find((n) => n.id === grp.id)!.data.collapsed).toBe(true)
+
+    info = computeCollapseInfo(result.current.nodes)
+    expect(info.visibleIds.has(grp.id)).toBe(true)
+    expect(info.visibleIds.has('c1')).toBe(false)
+    expect(info.visibleIds.has('c2')).toBe(false)
+    expect(info.hiddenBy.get('c1')).toBe(grp.id)
+  })
+})