Britain’s largest undeveloped oilfield has been thrown into limbo. Equinor’s Rosebank project, a $3.8 billion investment once known as the future backbone of UK energy security, has been suspended after regulators demanded new environmental approvals that account for the full carbon footprint of the oil and gas it would produce. What was supposed to be a flagship development on the UK Continental Shelf has instead become the clearest example yet of how legal challenges and climate politics are reshaping the fate of offshore hydrocarbons.…