fix(cli): honor the boolean config save contract in set commands

ConfigManager.save_to_file returns a bare bool, but every mesh CLI set
command (and the password command) still tuple-unpacked it, so each one
wrote the YAML and then raised, skipping the live update and returning an
error to the remote admin. Route every save through one helper that
checks the bool, reports save failures honestly, and only live-applies
after a successful write. The test fixture mocked the stale tuple shape,
which is why the suite stayed green while the CLI was broken on the real
manager.

tests/test_handler_helpers_mesh_cli.py

@@ -36,9 +36,9 @@ def _base_config():
     }
 
 
-def _cfg_mgr(save_ok=True, err=None):
+def _cfg_mgr(save_ok=True):
     return SimpleNamespace(
-        save_to_file=MagicMock(return_value=(save_ok, err)),
+        save_to_file=MagicMock(return_value=save_ok),
         live_update_daemon=MagicMock(),
     )
 
@@ -97,9 +97,10 @@ def test_cmd_password_save_success_failure_and_exception():
     assert cli_ok._cmd_password("password newpw") == "password now: newpw"
     ok_mgr.live_update_daemon.assert_called_once_with(["security"])
 
-    bad_mgr = _cfg_mgr(save_ok=False, err="disk")
+    bad_mgr = _cfg_mgr(save_ok=False)
     cli_bad = MeshCLI("/tmp/cfg.yaml", _base_config(), bad_mgr)
     assert "Failed to save config" in cli_bad._cmd_password("password x")
+    bad_mgr.live_update_daemon.assert_not_called()
 
     ex_mgr = SimpleNamespace(
         save_to_file=MagicMock(side_effect=RuntimeError("boom")),
@@ -442,3 +443,12 @@ def test_discovery_auto_add_skips_local_node_and_persists_remote():
     )
     assert remote_result["auto_added"] is True
     storage.record_advert.assert_called_once()
+
+
+def test_cmd_set_save_failure_reports_error_and_skips_live_update():
+    mgr = _cfg_mgr(save_ok=False)
+    cli = MeshCLI("/tmp/cfg.yaml", _base_config(), mgr)
+
+    for command in ("af 2.0", "name x", "freq 915", "guest.password g", "flood.max 8"):
+        assert cli._cmd_set(command) == "Error: Failed to save config"
+    mgr.live_update_daemon.assert_not_called()