docs: 统一公开 API 的中英双语注释

- 补齐公开接口说明段的英文描述，保持签名注释和详细说明均为中英双语结构
- 规范农历、坐标、公式、轨道、日晷、太阳、恒星及行星事件等 API 的注释口径

coord/airmass.go

@@ -5,6 +5,7 @@ import "b612.me/astro/formula"
 // AirmassPlaneParallelFromTrueAltitude 平行平板大气质量 / plane-parallel airmass from true altitude.
 //
 // 输入为真高度角，单位度。适合中高空几何近似，接近地平线时会发散。
+// Input is true altitude in degrees. This geometric approximation is suitable at moderate and high altitudes but diverges near the horizon.
 func AirmassPlaneParallelFromTrueAltitude(trueAltitude float64) float64 {
 	return formula.AirmassPlaneParallel(trueAltitude)
 }
@@ -12,6 +13,7 @@ func AirmassPlaneParallelFromTrueAltitude(trueAltitude float64) float64 {
 // AirmassKastenYoungFromApparentAltitude Kasten-Young 大气质量 / Kasten-Young airmass from apparent altitude.
 //
 // 输入为视高度角，单位度。
+// Input is apparent altitude in degrees.
 func AirmassKastenYoungFromApparentAltitude(apparentAltitude float64) float64 {
 	return formula.AirmassKastenYoung(apparentAltitude)
 }
@@ -19,6 +21,7 @@ func AirmassKastenYoungFromApparentAltitude(apparentAltitude float64) float64 {
 // AirmassPickeringFromApparentAltitude Pickering 大气质量 / Pickering airmass from apparent altitude.
 //
 // 输入为视高度角，单位度。
+// Input is apparent altitude in degrees.
 func AirmassPickeringFromApparentAltitude(apparentAltitude float64) float64 {
 	return formula.AirmassPickering(apparentAltitude)
 }
@@ -26,6 +29,7 @@ func AirmassPickeringFromApparentAltitude(apparentAltitude float64) float64 {
 // AirmassKastenYoungFromTrueAltitude Kasten-Young 大气质量 / Kasten-Young airmass from true altitude.
 //
 // 先用 pressureHPa / temperatureC 估算大气折射，将真高度角换算为视高度角，再代入经验公式。
+// First estimates atmospheric refraction from pressureHPa and temperatureC, converts true altitude to apparent altitude, and then applies the empirical formula.
 func AirmassKastenYoungFromTrueAltitude(trueAltitude, pressureHPa, temperatureC float64) float64 {
 	return formula.AirmassKastenYoung(ApparentAltitude(trueAltitude, pressureHPa, temperatureC))
 }
@@ -33,6 +37,7 @@ func AirmassKastenYoungFromTrueAltitude(trueAltitude, pressureHPa, temperatureC
 // AirmassPickeringFromTrueAltitude Pickering 大气质量 / Pickering airmass from true altitude.
 //
 // 先用 pressureHPa / temperatureC 估算大气折射，将真高度角换算为视高度角，再代入经验公式。
+// First estimates atmospheric refraction from pressureHPa and temperatureC, converts true altitude to apparent altitude, and then applies the empirical formula.
 func AirmassPickeringFromTrueAltitude(trueAltitude, pressureHPa, temperatureC float64) float64 {
 	return formula.AirmassPickering(ApparentAltitude(trueAltitude, pressureHPa, temperatureC))
 }