Four of the biggest US technology companies together have forecast capital expenditures that will reach about $650 billion in 2026 — a mind-boggling tide of cash earmarked for new data centers and the long list of equipment needed to make them tick, including artificial intelligence chips, networking cables and backup generators.The spending planned by Alphabet Inc., Amazon.com Inc., Meta Platforms Inc. and Microsoft Corp., all in pursuit of dominance in the still-nascent market for AI tools, is...