Implements a caching mechanism for the multi-timeframe (MTF) trend confirmation in `GetMTFDir`.
The trend direction from the lower timeframe is now calculated only when a new bar forms on that timeframe, instead of on every tick of the main chart. The result is cached and returned on subsequent calls until the next lower timeframe bar appears.
This avoids expensive and redundant `CopyBuffer` calls, significantly improving the EA's performance and efficiency, especially when the signal timeframe is much shorter than the confirmation timeframe. Logic was carefully updated to read from the last *completed* bar to prevent any change in trading behavior.
