Arrow keys on the Config view's server dropdowns

The form navigation recognised dropdowns only as *tview.DropDown, so on
the new profile and folder dropdowns ←→ did nothing and ↑↓ left an open
list instead of moving through it.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_019reK4DUGYqDUjniWYJvwUW

internal/ui/form.go

@@ -116,8 +116,13 @@ func focusedDropDown(f *tview.Form, item int) (*tview.DropDown, bool) {
 	if item < 0 {
 		return nil, false
 	}
-	dd, ok := f.GetFormItem(item).(*tview.DropDown)
-	return dd, ok
+	switch it := f.GetFormItem(item).(type) {
+	case *tview.DropDown:
+		return it, true
+	case *serverChoice: // a dropdown with extras; the keys work the same
+		return it.DropDown, true
+	}
+	return nil, false
 }
 
 // bindSearchNow keeps a "Search now" checkbox consistent with whether a search