fix(auth): update terminology to 'sign in' and 'sign out' (#20892)

Co-authored-by: Jacob Richman <jacob314@gmail.com>

packages/cli/src/ui/components/LogoutConfirmationDialog.tsx

@@ -37,7 +37,7 @@ export const LogoutConfirmationDialog: React.FC<
 
   const options: Array<RadioSelectItem<LogoutChoice>> = [
     {
-      label: 'Login',
+      label: 'Sign in',
       value: LogoutChoice.LOGIN,
       key: 'login',
     },
@@ -61,10 +61,10 @@ export const LogoutConfirmationDialog: React.FC<
       >
         <Box flexDirection="column" marginBottom={1}>
           <Text bold color={theme.text.primary}>
-            You are now logged out.
+            You are now signed out
           </Text>
           <Text color={theme.text.secondary}>
-            Login again to continue using Gemini CLI, or exit the application.
+            Sign in again to continue using Gemini CLI, or exit the application.
           </Text>
         </Box>