I asked CEO Sundar Pichai why he recently took Google free cash flow negative for the first time to ramp up AI capex. His answer: "It's not just hope." "To do something like this, you need to be confident on multiple levels. We are fortunate to have early signals from such a diversified opportunity set, all the way from consumer to enterprise. And so we are seeing those robust demand signals. We have the demand signal for Google itself, which is a cutting-edge enterprise in how we are using…