A plunge in the value of the Indian rupee to record lows over the past week as Asia’s worst-performing currency could be a mixed blessing for the South Asian economy, which has been gunning for months to reach a trade deal with the US, observers say.The Indian rupee has extended its slide to more than 90 against the US dollar this week, after breaching the 90-level mark last week.While the drop in the currency’s value will make everything from the country’s massive oil imports to the cost of...