Raff Channel regression

A trend channel indicator based on a rolling linear regression. Over a window of the last N closed candles, it computes the regression line (center line), then plots two parallel bands at a distance of coefficient × standard deviation of the residuals (the distance between each close and the regression line) on either side. The channel is recalculated on every new candle and displayed as a straight segment over the current window only — no curve, no retroactive recalculation across the whole history.