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/moon_bright_limb.go

@@ -0,0 +1,45 @@
+package basic
+
+import . "b612.me/astro/tools"
+
+// MoonBrightLimbPositionAngle 月亮明亮边缘位置角 / position angle of the Moon's bright limb.
+func MoonBrightLimbPositionAngle(jd float64) float64 {
+	return MoonBrightLimbPositionAngleN(jd, -1)
+}
+
+// MoonBrightLimbPositionAngleN 月亮明亮边缘位置角（截断版） / truncated position angle of the Moon's bright limb.
+func MoonBrightLimbPositionAngleN(jd float64, n int) float64 {
+	sunRA, sunDec := HSunApparentRaDecN(jd, n)
+	moonRA, moonDec := HMoonTrueRaDecN(jd, n)
+	return brightLimbPositionAngleFromRaDec(sunRA, sunDec, moonRA, moonDec)
+}
+
+// MoonTopocentricBrightLimbPositionAngle 月亮站心明亮边缘位置角 / topocentric position angle of the Moon's bright limb.
+func MoonTopocentricBrightLimbPositionAngle(jd, observerLon, observerLat, height float64) float64 {
+	return MoonTopocentricBrightLimbPositionAngleN(jd, observerLon, observerLat, height, -1)
+}
+
+// MoonTopocentricBrightLimbPositionAngleN 月亮站心明亮边缘位置角（截断版） / truncated topocentric position angle of the Moon's bright limb.
+func MoonTopocentricBrightLimbPositionAngleN(jd, observerLon, observerLat, height float64, n int) float64 {
+	sunRA, sunDec := sunTopocentricApparentRaDecN(jd, observerLon, observerLat, height, n)
+	moonRA, moonDec := moonTopocentricApparentRaDecN(jd, observerLon, observerLat, height, n)
+	return brightLimbPositionAngleFromRaDec(sunRA, sunDec, moonRA, moonDec)
+}
+
+func moonTopocentricApparentRaDecN(jd, observerLon, observerLat, height float64, n int) (float64, float64) {
+	geocentricRA := HMoonTrueRaN(jd, n)
+	geocentricDec := HMoonTrueDecN(jd, n)
+	distanceAU := HMoonAwayN(jd, n) / moonPhysicalAstronomicalUnitKM
+	return TopocentricRaDec(geocentricRA, geocentricDec, observerLat, observerLon, TD2UT(jd, false), distanceAU, height)
+}
+
+func sunTopocentricApparentRaDecN(jd, observerLon, observerLat, height float64, n int) (float64, float64) {
+	geocentricRA, geocentricDec := HSunApparentRaDecN(jd, n)
+	return TopocentricRaDec(geocentricRA, geocentricDec, observerLat, observerLon, TD2UT(jd, false), EarthAwayN(jd, n), height)
+}
+
+func brightLimbPositionAngleFromRaDec(sunRA, sunDec, bodyRA, bodyDec float64) float64 {
+	y := Cos(sunDec) * Sin(sunRA-bodyRA)
+	x := Sin(sunDec)*Cos(bodyDec) - Cos(sunDec)*Sin(bodyDec)*Cos(sunRA-bodyRA)
+	return ArcTan2(y, x)
+}