feat(FN-3005): merge fusion/fn-3005

Commits merged:
- fix(FN-3005): restore dashboard typecheck for custom providers
- feat(FN-3005): complete Step 1 — use explicit mode labels
- test(FN-3005): complete Step 3 — assert explicit mode toggle labels
- feat(FN-3005): complete Step 2 — fit explicit mode labels in header

Files changed:
packages/dashboard/app/components/ModelOnboardingModal.tsx        | 2 +-
 packages/dashboard/app/components/QuickChatFAB.css                | 4 ++--
 packages/dashboard/app/components/QuickChatFAB.tsx                | 4 ++--
 packages/dashboard/app/components/SettingsModal.tsx               | 6 +++---
 packages/dashboard/app/components/__tests__/QuickChatFAB.test.tsx | 4 ++--
 5 files changed, 10 insertions(+), 10 deletions(-)

Fusion-Task-Id: FN-3005

packages/dashboard/app/components/QuickChatFAB.css

@@ -239,11 +239,10 @@
 }
 
 .quick-chat-mode-btn {
-  width: var(--quick-chat-header-control-size);
   min-width: var(--quick-chat-header-control-size);
   height: var(--quick-chat-header-control-size);
   min-height: var(--quick-chat-header-control-size);
-  padding: 0;
+  padding: 0 var(--space-sm);
   display: inline-flex;
   align-items: center;
   justify-content: center;
@@ -256,6 +255,7 @@
   line-height: 1;
   cursor: pointer;
   transition: var(--transition-fast);
+  white-space: nowrap;
 }
 
 .quick-chat-new-chat-btn {