Phase 006: migrate the chat page from naive-ui to Arco Design Vue

Swaps the rendering layer only. Chat store logic, keyboard handling, and the
/chat-run Socket.IO contract are untouched, so a mixed UI cannot hide a chat
regression behind a library swap.

Arco's dropdowns take their items from a #content slot of a-doption children
rather than a droplist prop, and Arco Triggers cannot be nested, so the two
toolbar menus lost their a-tooltip in favour of a native title. Both rules are
recorded in docs/arco-mapping.md, and tests/e2e/chat-input-dropdown.spec.ts plus
tests/e2e/chat-rendering-smoke.spec.ts keep the menus, the streaming markdown
rendering, and the no-Arco-inside-the-bubble red line from regressing silently.

tests/client/session-search.test.ts

@@ -1,7 +1,7 @@
 // @vitest-environment jsdom
 import { nextTick, defineComponent, h } from 'vue'
 import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
-import { mount } from '@vue/test-utils'
+import { config, mount } from '@vue/test-utils'
 
 const apiMocks = vi.hoisted(() => ({
   fetchSessionsMock: vi.fn(),
@@ -40,31 +40,32 @@ vi.mock('vue-i18n', () => ({
   }),
 }))
 
-vi.mock('naive-ui', async () => {
-  const actual = await vi.importActual<any>('naive-ui')
-  return {
-    ...actual,
-    useMessage: () => ({
-      error: vi.fn(),
-    }),
-    NModal: {
-      props: ['show'],
-      emits: ['update:show'],
-      template: '<div v-if="show" class="n-modal-stub"><slot /></div>',
-    },
-    NInput: {
-      props: ['value', 'size'],
-      emits: ['update:value', 'keydown'],
-      template: '<input class="n-input-stub" :value="value" @input="$emit(\'update:value\', $event.target.value)" @keydown="$emit(\'keydown\', $event)" />',
-    },
-    NSpin: {
-      template: '<div class="n-spin-stub"><slot /></div>',
-    },
-    NButton: {
-      template: '<button class="n-button-stub"><slot /></button>',
-    },
-  }
-})
+// The search modal teleports to body in jsdom, so stub the overlays to render
+// inline and keep the DOM shape the assertions below rely on.
+config.global.stubs = {
+  AModal: {
+    name: 'AModal',
+    props: ['visible'],
+    emits: ['update:visible'],
+    template: '<div v-if="visible" class="a-modal-stub"><slot /></div>',
+  },
+  AInput: {
+    name: 'AInput',
+    // `size` is an Arco prop, not an HTML input attribute; declaring it keeps
+    // it off the native element.
+    props: ['modelValue', 'size'],
+    emits: ['update:modelValue'],
+    template: '<input class="a-input-stub" :value="modelValue" @input="$emit(\'update:modelValue\', $event.target.value)" />',
+  },
+  ASpin: {
+    name: 'ASpin',
+    template: '<div class="a-spin-stub"><slot /></div>',
+  },
+  AButton: {
+    name: 'AButton',
+    template: '<button class="a-button-stub"><slot /></button>',
+  },
+}
 
 import SessionSearchModal from '@/components/hermes/chat/SessionSearchModal.vue'
 import { useSessionSearch } from '@/composables/useSessionSearch'
@@ -167,7 +168,7 @@ describe('session search modal', () => {
     await flushPromises()
     await nextTick()
 
-    const input = wrapper.find('input.n-input-stub')
+    const input = wrapper.find('input.a-input-stub')
     await input.setValue('docker')
     await vi.advanceTimersByTimeAsync(200)
     await flushPromises()