add error message for save failure

Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

Author: skarim

cmd/utils.go

@@ -1094,6 +1094,8 @@ func pickRemote(cfg *config.Config, branch, remoteOverride string) (string, erro
 			cfg.Successf("Saved %q as the default remote for gh stack", selectedRemote)
 			cfg.Printf("To change later, run: %s", cfg.ColorCyan("git config gh-stack.remote <other-remote>"))
 			cfg.Printf("To clear, run:        %s", cfg.ColorCyan("git config --unset gh-stack.remote"))
+		} else {
+			cfg.Warningf("Could not save remote preference: %v", saveErr)
 		}
 	}
 

internal/git/git.go

@@ -191,7 +191,7 @@ func SaveRerereDeclined() error {
 }
 
 // GetSavedRemote returns the remote saved via gh-stack.remote git config,
-// or an empty string if none is saved.
+// or an error if none is configured.
 func GetSavedRemote() (string, error) {
 	return ops.GetSavedRemote()
 }