- fix: Correct sun.TrueBo calculation, now using basic.HSunTrueBo for correct solar latitude

- fix: Rename GetSunDownTime to GetSunSetTime in basic/sun.go and update related calls/outputs
- fix: Update test cases to use new method and error constant names

- improve: Rename all DownTime/Down functions to SetTime/Set for consistency
- improve: Standardize ERR_XXX_NEVER_DOWN error constants to ERR_XXX_NEVER_SET, with ERR_XXX_NEVER_DOWN kept as compatibility alias
- improve: More standard naming for interfaces and errors to improve maintainability and readability

sun/sun.go

@@ -10,7 +10,7 @@ import (
 var (
 	ERR_SUN_NEVER_RISE = errors.New("ERROR:极夜，太阳在今日永远在地平线下！")
 	ERR_SUN_NEVER_SET  = errors.New("ERROR:极昼，太阳在今日永远在地平线上！")
-	// ERR_SUN_NEVER_DOWN deprecated -- use ERR_SUN_NEVER_RISE instead
+	// ERR_SUN_NEVER_DOWN deprecated: -- use ERR_SUN_NEVER_RISE instead
 	ERR_SUN_NEVER_DOWN      = ERR_SUN_NEVER_SET
 	ERR_TWILIGHT_NOT_EXISTS = errors.New("ERROR:今日晨昏朦影不存在！")
 )
@@ -54,7 +54,7 @@ func RiseTime(date time.Time, lon, lat, height float64, aero bool) (time.Time, e
 	return basic.JDE2DateByZone(riseJde, date.Location(), true), err
 }
 
-// deprecated -- use SetTime instead
+// deprecated: -- use SetTime instead
 // DownTime 太阳落下时间
 // date，当地时区日期，务必做时区修正
 // lon，经度，东正西负