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/styles/global.scss

@@ -259,14 +259,14 @@ a {
 }
 
 // Prevent iOS Safari auto-zoom on input focus by ensuring font-size is at least 16px
+// Arco 的 a-input 渲染原生 <input>，已被上面的元素选择器覆盖；
+// 需要额外兜住的是 a-textarea（渲染 textarea，字体继承自容器）与 Arco 包装层。
 @media (max-width: 768px) {
   input,
   textarea,
   select,
-  .n-input,
-  .n-input__input-element,
-  .n-input__textarea-el,
-  .n-input__textarea-element {
+  .arco-input,
+  .arco-textarea {
     font-size: 16px !important;
   }
 }