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/chat/ChatPanel.vue

@@ -2614,7 +2614,7 @@ async function handleSessionModelCustomSubmit() {
 
 .default-workspace-label {
   font-size: 13px;
-  color: var(--n-text-color-3);
+  color: var(--text-muted);
   flex-shrink: 0;
 }
 
@@ -2655,7 +2655,7 @@ async function handleSessionModelCustomSubmit() {
 }
 
 .workspace-chip-separator {
-  color: var(--n-text-color-3);
+  color: var(--text-muted);
   font-size: 13px;
   user-select: none;
 }
@@ -2711,7 +2711,7 @@ async function handleSessionModelCustomSubmit() {
 }
 
 .workspace-dropdown-item:hover {
-  background: var(--n-color-hover);
+  background: var(--bg-card-hover);
 }
 
 .workspace-default-badge {