feat: 扩展天文计算能力

- 新增日食、月食、本地可见性、中心线、半影区域、SVG 图示与沙罗周期信息
- 新增行星冲合、留、方照、物理星历、视直径、相位、亮肢角、轨道节点等计算
- 新增木星伽利略卫星位置、现象与接触事件计算
- 新增恒星星表、星座判定、自行修正与观测辅助能力
- 新增 coord、formula、orbit、sundial、lite/sun、lite/moon 等扩展包
- 完善农历年号、月相英文别名、视差角、大气质量、折射、日晷与双星计算
- 增加 NASA、JPL Horizons、IMCCE 等回归测试数据与基线测试
- 重构基础算法文件组织，补充大量公开 API 注释和语义回归测试
- 更新中文和英文 README，补充示例、精度说明、SVG 配图

basic/diameter.go

@@ -0,0 +1,206 @@
+package basic
+
+import "math"
+
+const (
+	angularDiameterAstronomicalUnitKM = 149597870.7
+	angularDiameterArcsecPerRadian    = 180.0 * 3600.0 / math.Pi
+
+	sunEquatorialRadiusKM     = 695700.0
+	moonEquatorialRadiusKM    = 1737.4
+	mercuryEquatorialRadiusKM = 2440.53
+	venusEquatorialRadiusKM   = 6051.8
+	marsEquatorialRadiusKM    = 3396.19
+	jupiterEquatorialRadiusKM = 71492.0
+	saturnEquatorialRadiusKM  = 60268.0
+	uranusEquatorialRadiusKM  = 25559.0
+	neptuneEquatorialRadiusKM = 24764.0
+)
+
+func angularSemidiameterArcsec(radiusKM, distanceKM float64) float64 {
+	return math.Asin(radiusKM/distanceKM) * angularDiameterArcsecPerRadian
+}
+
+func angularSemidiameterFromAU(radiusKM, distanceAU float64) float64 {
+	return angularSemidiameterArcsec(radiusKM, distanceAU*angularDiameterAstronomicalUnitKM)
+}
+
+// SunSemidiameter 太阳视半径，单位角秒 / apparent solar semidiameter in arcseconds.
+func SunSemidiameter(jd float64) float64 {
+	return SunSemidiameterN(jd, -1)
+}
+
+// SunSemidiameterN 太阳视半径（截断版），单位角秒 / truncated apparent solar semidiameter in arcseconds.
+func SunSemidiameterN(jd float64, n int) float64 {
+	return angularSemidiameterFromAU(sunEquatorialRadiusKM, EarthAwayN(jd, n))
+}
+
+// SunDiameter 太阳视直径，单位角秒 / apparent solar diameter in arcseconds.
+func SunDiameter(jd float64) float64 {
+	return SunDiameterN(jd, -1)
+}
+
+// SunDiameterN 太阳视直径（截断版），单位角秒 / truncated apparent solar diameter in arcseconds.
+func SunDiameterN(jd float64, n int) float64 {
+	return 2 * SunSemidiameterN(jd, n)
+}
+
+// MoonSemidiameter 月亮视半径，单位角秒 / apparent lunar semidiameter in arcseconds.
+func MoonSemidiameter(jd float64) float64 {
+	return MoonSemidiameterN(jd, -1)
+}
+
+// MoonSemidiameterN 月亮视半径（截断版），单位角秒 / truncated apparent lunar semidiameter in arcseconds.
+func MoonSemidiameterN(jd float64, n int) float64 {
+	return angularSemidiameterArcsec(moonEquatorialRadiusKM, HMoonAwayN(jd, n))
+}
+
+// MoonDiameter 月亮视直径，单位角秒 / apparent lunar diameter in arcseconds.
+func MoonDiameter(jd float64) float64 {
+	return MoonDiameterN(jd, -1)
+}
+
+// MoonDiameterN 月亮视直径（截断版），单位角秒 / truncated apparent lunar diameter in arcseconds.
+func MoonDiameterN(jd float64, n int) float64 {
+	return 2 * MoonSemidiameterN(jd, n)
+}
+
+// MercurySemidiameter 水星视半径，单位角秒 / apparent Mercury semidiameter in arcseconds.
+func MercurySemidiameter(jd float64) float64 {
+	return MercurySemidiameterN(jd, -1)
+}
+
+// MercurySemidiameterN 水星视半径（截断版），单位角秒 / truncated apparent Mercury semidiameter in arcseconds.
+func MercurySemidiameterN(jd float64, n int) float64 {
+	return angularSemidiameterFromAU(mercuryEquatorialRadiusKM, EarthMercuryAwayN(jd, n))
+}
+
+// MercuryDiameter 水星视直径，单位角秒 / apparent Mercury diameter in arcseconds.
+func MercuryDiameter(jd float64) float64 {
+	return MercuryDiameterN(jd, -1)
+}
+
+// MercuryDiameterN 水星视直径（截断版），单位角秒 / truncated apparent Mercury diameter in arcseconds.
+func MercuryDiameterN(jd float64, n int) float64 {
+	return 2 * MercurySemidiameterN(jd, n)
+}
+
+// VenusSemidiameter 金星视半径，单位角秒 / apparent Venus semidiameter in arcseconds.
+func VenusSemidiameter(jd float64) float64 {
+	return VenusSemidiameterN(jd, -1)
+}
+
+// VenusSemidiameterN 金星视半径（截断版），单位角秒 / truncated apparent Venus semidiameter in arcseconds.
+func VenusSemidiameterN(jd float64, n int) float64 {
+	return angularSemidiameterFromAU(venusEquatorialRadiusKM, EarthVenusAwayN(jd, n))
+}
+
+// VenusDiameter 金星视直径，单位角秒 / apparent Venus diameter in arcseconds.
+func VenusDiameter(jd float64) float64 {
+	return VenusDiameterN(jd, -1)
+}
+
+// VenusDiameterN 金星视直径（截断版），单位角秒 / truncated apparent Venus diameter in arcseconds.
+func VenusDiameterN(jd float64, n int) float64 {
+	return 2 * VenusSemidiameterN(jd, n)
+}
+
+// MarsSemidiameter 火星视半径，单位角秒 / apparent Mars semidiameter in arcseconds.
+func MarsSemidiameter(jd float64) float64 {
+	return MarsSemidiameterN(jd, -1)
+}
+
+// MarsSemidiameterN 火星视半径（截断版），单位角秒 / truncated apparent Mars semidiameter in arcseconds.
+func MarsSemidiameterN(jd float64, n int) float64 {
+	return angularSemidiameterFromAU(marsEquatorialRadiusKM, EarthMarsAwayN(jd, n))
+}
+
+// MarsDiameter 火星视直径，单位角秒 / apparent Mars diameter in arcseconds.
+func MarsDiameter(jd float64) float64 {
+	return MarsDiameterN(jd, -1)
+}
+
+// MarsDiameterN 火星视直径（截断版），单位角秒 / truncated apparent Mars diameter in arcseconds.
+func MarsDiameterN(jd float64, n int) float64 {
+	return 2 * MarsSemidiameterN(jd, n)
+}
+
+// JupiterSemidiameter 木星视半径，单位角秒 / apparent Jupiter semidiameter in arcseconds.
+func JupiterSemidiameter(jd float64) float64 {
+	return JupiterSemidiameterN(jd, -1)
+}
+
+// JupiterSemidiameterN 木星视半径（截断版），单位角秒 / truncated apparent Jupiter semidiameter in arcseconds.
+func JupiterSemidiameterN(jd float64, n int) float64 {
+	return angularSemidiameterFromAU(jupiterEquatorialRadiusKM, EarthJupiterAwayN(jd, n))
+}
+
+// JupiterDiameter 木星视直径，单位角秒 / apparent Jupiter diameter in arcseconds.
+func JupiterDiameter(jd float64) float64 {
+	return JupiterDiameterN(jd, -1)
+}
+
+// JupiterDiameterN 木星视直径（截断版），单位角秒 / truncated apparent Jupiter diameter in arcseconds.
+func JupiterDiameterN(jd float64, n int) float64 {
+	return 2 * JupiterSemidiameterN(jd, n)
+}
+
+// SaturnSemidiameter 土星视半径，单位角秒 / apparent Saturn semidiameter in arcseconds.
+func SaturnSemidiameter(jd float64) float64 {
+	return SaturnSemidiameterN(jd, -1)
+}
+
+// SaturnSemidiameterN 土星视半径（截断版），单位角秒 / truncated apparent Saturn semidiameter in arcseconds.
+func SaturnSemidiameterN(jd float64, n int) float64 {
+	return angularSemidiameterFromAU(saturnEquatorialRadiusKM, EarthSaturnAwayN(jd, n))
+}
+
+// SaturnDiameter 土星视直径，单位角秒 / apparent Saturn diameter in arcseconds.
+func SaturnDiameter(jd float64) float64 {
+	return SaturnDiameterN(jd, -1)
+}
+
+// SaturnDiameterN 土星视直径（截断版），单位角秒 / truncated apparent Saturn diameter in arcseconds.
+func SaturnDiameterN(jd float64, n int) float64 {
+	return 2 * SaturnSemidiameterN(jd, n)
+}
+
+// UranusSemidiameter 天王星视半径，单位角秒 / apparent Uranus semidiameter in arcseconds.
+func UranusSemidiameter(jd float64) float64 {
+	return UranusSemidiameterN(jd, -1)
+}
+
+// UranusSemidiameterN 天王星视半径（截断版），单位角秒 / truncated apparent Uranus semidiameter in arcseconds.
+func UranusSemidiameterN(jd float64, n int) float64 {
+	return angularSemidiameterFromAU(uranusEquatorialRadiusKM, EarthUranusAwayN(jd, n))
+}
+
+// UranusDiameter 天王星视直径，单位角秒 / apparent Uranus diameter in arcseconds.
+func UranusDiameter(jd float64) float64 {
+	return UranusDiameterN(jd, -1)
+}
+
+// UranusDiameterN 天王星视直径（截断版），单位角秒 / truncated apparent Uranus diameter in arcseconds.
+func UranusDiameterN(jd float64, n int) float64 {
+	return 2 * UranusSemidiameterN(jd, n)
+}
+
+// NeptuneSemidiameter 海王星视半径，单位角秒 / apparent Neptune semidiameter in arcseconds.
+func NeptuneSemidiameter(jd float64) float64 {
+	return NeptuneSemidiameterN(jd, -1)
+}
+
+// NeptuneSemidiameterN 海王星视半径（截断版），单位角秒 / truncated apparent Neptune semidiameter in arcseconds.
+func NeptuneSemidiameterN(jd float64, n int) float64 {
+	return angularSemidiameterFromAU(neptuneEquatorialRadiusKM, EarthNeptuneAwayN(jd, n))
+}
+
+// NeptuneDiameter 海王星视直径，单位角秒 / apparent Neptune diameter in arcseconds.
+func NeptuneDiameter(jd float64) float64 {
+	return NeptuneDiameterN(jd, -1)
+}
+
+// NeptuneDiameterN 海王星视直径（截断版），单位角秒 / truncated apparent Neptune diameter in arcseconds.
+func NeptuneDiameterN(jd float64, n int) float64 {
+	return 2 * NeptuneSemidiameterN(jd, n)
+}