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

tests/e2e/provider-models.spec.ts

@@ -22,7 +22,12 @@ test('fetches custom provider models through the backend proxy', async ({ page }
   await page.getByRole('button', { name: 'Fetch' }).click()
 
   await expect(page.getByText('Found 2 models')).toBeVisible()
-  await expect(page.getByText('proxy-model-a')).toBeVisible()
+  // Scope to the dropdown options: Arco renders both the select's current value
+  // and the option list, so a bare text match resolves to two nodes. The option
+  // list is collapsed by this point, so assert presence rather than visibility.
+  await expect(
+    page.locator('.arco-select-option-content', { hasText: 'proxy-model-a' }),
+  ).toHaveCount(1)
 
   const proxyRequest = api.requests.find((request) => request.pathname === '/api/hermes/provider-models')
   expect(proxyRequest).toBeTruthy()