Phase 007: migrate every remaining view from naive-ui to Arco Design Vue

The project now has exactly one UI library. Every naive-ui component in
packages/client/src is replaced by its Arco equivalent across 24 views and
roughly 80 components, and naive-ui is dropped from package.json along with
its transitive vueuc / @css-render / vdirs / seemly dependencies.

The migration is rendering-layer only. No store logic, no API contract, and
no /chat-run payload was touched.

Three classes of leftover were invisible to `grep naive-ui` and are now
covered by tests/client/no-naive-ui.test.ts, which asserts all three:
  - dead .n-* class names in style blocks
  - dead --n-* custom properties
  - naive-ui in package.json

Notable behavioural traps handled along the way, recorded in
docs/arco-migration-rules.md:
  - a-input-password defaults to masked; passing default-visibility="false"
    would have exposed API keys in clear text
  - a-upload fires a real XHR unless auto-upload is false
  - nested Trigger components fight over the first element child, so the
    group-chat settings dropdown was flattened
  - Arco renders tooltip default-slot text inline, which was silently
    collapsing the chat and group-chat toolbars

packages/client/src/components/hermes/settings/PrivacySettings.vue

@@ -1,5 +1,4 @@
 <script setup lang="ts">
-import { NSwitch } from 'naive-ui'
 import { useMessage } from '@/composables/useMessage'
 import { useI18n } from 'vue-i18n'
 import { useSettingsStore } from '@/stores/hermes/settings'
@@ -22,7 +21,7 @@ async function save(values: Record<string, any>) {
 <template>
   <section class="settings-section">
     <SettingRow :label="t('settings.privacy.redactPii')" :hint="t('settings.privacy.redactPiiHint')">
-      <NSwitch :value="settingsStore.privacy.redact_pii" @update:value="v => save({ redact_pii: v })" />
+      <a-switch :model-value="settingsStore.privacy.redact_pii" @update:model-value="v => save({ redact_pii: v })" />
     </SettingRow>
   </section>
 </template>