test: Improve TestSSH/ForwardAgent stability on macOS (#5745)

cli/ssh_test.go

@@ -274,6 +274,10 @@ func TestSSH(t *testing.T) {
 			assert.NoError(t, err, "ssh command failed")
 		})
 
+		// Wait for the prompt or any output really to indicate the command has
+		// started and accepting input on stdin.
+		_ = pty.Peek(ctx, 1)
+
 		// Ensure that SSH_AUTH_SOCK is set.
 		// Linux: /tmp/auth-agent3167016167/listener.sock
 		// macOS: /var/folders/ng/m1q0wft14hj0t3rtjxrdnzsr0000gn/T/auth-agent3245553419/listener.sock