fix(plotting): 风速时序图增加 winddir 通道

_time_series_wrapper 的 ys 参数从 ['windspeed'] 改为 ['windspeed', 'winddir']，
双Y轴分别显示风速 (m/s) 和风向 (°)

src/gasflux/plotting.py

@@ -632,14 +632,14 @@ def _windrose_wrapper(df):
 
 
 def _time_series_wrapper(df):
-    """time_series(df) → original time_series(df, ys=['windspeed'])"""
+    """time_series(df) → original time_series(df, ys=['windspeed','winddir'])"""
     return time_series(
         df,
-        ys=["windspeed"],
+        ys=["windspeed", "winddir"],
         x="timestamp",
         rolling_average=True,
         scatter=True,
-        y_titles="Wind Speed (m/s)",
+        y_titles=["Wind Speed (m/s)", "Wind Direction (°)"],
     )