Increase ssh command timeout and improve error message

- My `github/github` codespace failed to start within 10s
- Output more precise error message

cmd/ghcs/ssh.go

@@ -111,8 +111,8 @@ func SSH(sshProfile string) error {
 			time.Sleep(1 * time.Second)
 		}
 
-		if retries == 10 {
-			return errors.New("Failed to start codespace")
+		if retries == 30 {
+			return errors.New("timed out while waiting for the codespace to start")
 		}
 
 		codespace, err = apiClient.GetCodespace(ctx, token, codespace.OwnerLogin, codespace.Name)