PARIS — Emmanuel Macron and Friedrich Merz are trying to jump-start the Franco-German engine one final time. After joint ministerial meetings in Germany last week, the leaders of the European Union’s two biggest economies have tasked their governments with striking a grand bargain that they say would strengthen Europe’s industrial defenses and revive the bloc’s automotive industry — key priorities for the two countries. The pact would fuse France’s push to reserve more public procurement contracts and subsidies for European industry with Germany’s drive to rescue its ailing carmakers, whose crisis has reached an acute stage after Volkswagen warned recently...