The models.dev deepseek branch publishes the official OFF-PEAK rates
(deepseek-flash: 0.15/0.6/0.003 USD per 1M = api-docs.deepseek.com's
valley tier), but the estimator read the book as the peak list and then
halved the off bucket — every DeepSeek session under-estimated ~2x in
both periods. Flip the semantics: DeepSeek's peak bucket prices at
twice the book rate and the off bucket at book; the tooltip's peak
column doubles for DeepSeek rows with its structure untouched, so
deepseek-flash now reproduces the official peak|off-peak list exactly.
Fixes#78