SAN JOSE — A San Jose housing tower that once was touted by local leaders as a future lively downtown hub was foreclosed over a failed loan in a financial setback that shows the high-rise’s value has nosedived. “The Fay being seized by its lender is another clear signal of how fragile high-rise housing economics have become in downtown San Jose,” said Bob Staedler, principal executive with Silicon Valley Synergy, a land-use consultancy. San Jose officials expressed hope at the time that the hundreds of people who would potentially live in The Fay would be able to contribute to a more lively downtown. For the moment, the Fay’s financial failure helps to create a murky situation regarding near-term development in downtown San Jose. “It raises real questions about how many downtown towers can realistically move forward under today’s conditions,” Staedler said.