fix(lint): mode:'file' for the components-foundation Icon.vue bridge

Plan-1 Task-4 added { type:'components-foundation', pattern:
'src/components/Icon.vue' } without mode:'file'. eslint-plugin-boundaries
defaults to folder mode, so the single-file pattern never matched and
Icon.vue fell through to the generic `components` catch-all — breaking
the sanctioned components-v2 -> Icon bridge (RFC AD-G5) for every v2
shell component. Plan-1's boundary test only exercised the forms/**
folder-glob edge so the gap was latent. Adds mode:'file' + a regression
test locking the components-v2 -> Icon.vue edge.

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

apps/app/tests/unit/boundaries-v2.spec.ts

@@ -38,6 +38,18 @@ describe('boundaries — v2 zones', () => {
     expect(errs).toHaveLength(0)
   })
 
+  it('allows components-v2 → components-foundation (Icon.vue bridge, single-file mode:file)', async () => {
+    // Regression lock: the single-file element needs mode:'file' or
+    // Icon.vue falls through to the generic `components` catch-all and
+    // every v2 shell component's Icon import breaks (RFC AD-G5 bridge).
+    const errs = await boundaryErrors(
+      'src/components-v2/layout/SidebarNav.vue',
+      '<script setup lang="ts">import Icon from \'@/components/Icon.vue\'</script><template><Icon name="x" /></template>',
+    )
+
+    expect(errs).toHaveLength(0)
+  })
+
   it('allows components-v2 → components-foundation (FormField bridge)', async () => {
     const errs = await boundaryErrors(
       'src/components-v2/forms/Demo.vue',