BRUSSELS — An EU summit once billed as a chance to boost the bloc’s economy is now a full-blown stress test. Leaders gathering Thursday face a combustible agenda: Ukraine’s financial survival, Middle East escalation, transatlantic tensions, and deep internal rifts over energy and climate policy. Thursday’s meeting has been dramatically reshaped in recent days by the U.S.-Israeli war in Iran and a standoff with Hungary over a €90 billion lifeline for Kyiv — turning what had been meant to be a