feat(layouts): add OrganizerLayoutV2 + AppShellV2 skeleton

Tailwind-grid shell skeleton with named slot regions (sidebar, topbar,
default, drawer). OrganizerLayoutV2 wires the skeleton with RouterView,
selectable via definePage meta. Vitest component mount test: 2 tests pass.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

apps/app/tests/component/layouts/AppShellV2.spec.ts

@@ -0,0 +1,34 @@
+import { describe, expect, it } from 'vitest'
+import { mount } from '@vue/test-utils'
+import { createPinia } from 'pinia'
+import AppShellV2 from '@/layouts/components/AppShellV2.vue'
+
+describe('AppShellV2 (skeleton)', () => {
+  it('renders the grid regions and default slot content', () => {
+    const wrapper = mount(AppShellV2, {
+      global: { plugins: [createPinia()] },
+      slots: {
+        sidebar: '<nav data-testid="sb">SB</nav>',
+        topbar: '<header data-testid="tb">TB</header>',
+        default: '<main data-testid="content">CONTENT</main>',
+        drawer: '<aside data-testid="dr">DR</aside>',
+      },
+    })
+
+    expect(wrapper.find('[data-testid="appshell-v2"]').exists()).toBe(true)
+    expect(wrapper.find('[data-testid="sb"]').exists()).toBe(true)
+    expect(wrapper.find('[data-testid="tb"]').exists()).toBe(true)
+    expect(wrapper.find('[data-testid="content"]').text()).toBe('CONTENT')
+    expect(wrapper.find('[data-testid="dr"]').exists()).toBe(true)
+  })
+
+  it('applies the collapsed modifier from useShellUiStore', async () => {
+    const pinia = createPinia()
+    const wrapper = mount(AppShellV2, { global: { plugins: [pinia] } })
+    const { useShellUiStore } = await import('@/stores/useShellUiStore')
+
+    useShellUiStore().toggleSidebar()
+    await wrapper.vm.$nextTick()
+    expect(wrapper.find('[data-testid="appshell-v2"]').classes()).toContain('is-collapsed')
+  })
+})