For most of this century, rich countries have enjoyed a seemingly free lunch: They could spend money as needed, cut taxes at will and stimulate their way out of problems without paying a price in the form of higher borrowing costs or inflation. The big picture: That era is over. The $145 trillion global bond market is flashing red signals that there's now a price to be paid for governments that indulge their profligate impulses. It reflects a world where supply disruptions are colliding with massive government borrowing needs and the funds required for the AI buildout. The result: Higher inflation and surging demand for capital add up to higher and more volatile interest rates. State of play: In the near term, it becomes more expensive for American homebuyers and companies to borrow. In the medium term, it means a world of thornier trade-offs for policymakers.…