feat: 引入可切换星历模型并扩展天象观测链路

- 新增半解析、旧模型、自定义与多源堆叠星历实例，提供 Context、Instance、SPK 读取及状态与视位置计算
- 统一太阳、月球和行星实例接口，扩展黄经穿越、留、相位、最近角距、偕日可见、任意高度升落、轨道节点及凌日等天象查询
- 完善日月食、月掩与凌日的月缘剖面、有限盘面接触、站心修正、局地可见性、全球路径和地图输出
- 新增 SVG、GeoJSON、KML 天象输出及凌日、月掩和月缘地形相关缓存与几何求解
- 新增恒星星表导入与查询，支持 CSV、Hipparcos、BSC5、Stellarium 等格式及名称、交叉标识、锥面检索和星等过滤
- 补充 IAU 2006、地球定向、折射消光、大气观测、轨道传播及半解析行星/月球数据支持
- 将默认未来民用时标切换为 TimeScaleLeapHour，更新 2027–2400 农历速查表、中文日期解析和时区边界处理
- 增加事件基线、跨模型回归、几何边界、月缘地形和输出契约测试，完善中英文手册、示例资源、NOTICE 与忽略规则

geojson/occultation.go

@@ -5,7 +5,7 @@ import (
 	"math"
 	"time"
 
-	"b612.me/astro"
+	"b612.me/astro/basic"
 	"b612.me/astro/internal/geodata"
 	"b612.me/astro/internal/occultationgeo"
 	"b612.me/astro/moon"
@@ -124,7 +124,7 @@ func marshalStarOccultation(path moon.StarOccultationPath, markerOptions *TimeMa
 	if scaleErr != nil {
 		return nil, scaleErr
 	}
-	if timeScale == astro.TimeScaleUT1 {
+	if timeScale == basic.TimeScaleUT1 {
 		path = moon.StarOccultationPathInUT1(path)
 	}
 	if err := validateStarOccultationPathData(path); err != nil {
@@ -269,7 +269,7 @@ func marshalPlanetOccultation(path moon.PlanetOccultationPath, markerOptions *Ti
 	if scaleErr != nil {
 		return nil, scaleErr
 	}
-	if timeScale == astro.TimeScaleUT1 {
+	if timeScale == basic.TimeScaleUT1 {
 		path = moon.PlanetOccultationPathInUT1(path)
 	}
 	if err := path.Planet.Validate(); err != nil {
@@ -846,7 +846,7 @@ func occultationNearestRingVertex(
 	index := -1
 	distance := math.Inf(1)
 	for candidate, value := range ring {
-		current := occultationGeoDistanceKM(point, value)
+		current := geodata.EquatorialDistanceKM(point, value)
 		if current < distance {
 			index, distance = candidate, current
 		}
@@ -862,7 +862,7 @@ func occultationRingPathLengthKM(ring []geodata.GeoPoint, start, end, direction
 	index := start
 	for index != end {
 		next := (index + direction + len(ring)) % len(ring)
-		length += occultationGeoDistanceKM(ring[index], ring[next])
+		length += geodata.EquatorialDistanceKM(ring[index], ring[next])
 		index = next
 		if length > 1e8 {
 			return math.Inf(1)
@@ -873,7 +873,7 @@ func occultationRingPathLengthKM(ring []geodata.GeoPoint, start, end, direction
 
 func occultationRingEdgesWithinKM(ring []geodata.GeoPoint, maximum float64) bool {
 	for index := 1; index < len(ring); index++ {
-		if occultationGeoDistanceKM(ring[index-1], ring[index]) > maximum {
+		if geodata.EquatorialDistanceKM(ring[index-1], ring[index]) > maximum {
 			return false
 		}
 	}
@@ -883,23 +883,11 @@ func occultationRingEdgesWithinKM(ring []geodata.GeoPoint, maximum float64) bool
 func occultationGeoLineLengthKM(points []geodata.GeoPoint) float64 {
 	length := 0.0
 	for index := 1; index < len(points); index++ {
-		length += occultationGeoDistanceKM(points[index-1], points[index])
+		length += geodata.EquatorialDistanceKM(points[index-1], points[index])
 	}
 	return length
 }
 
-func occultationGeoDistanceKM(first, second geodata.GeoPoint) float64 {
-	const radiusKM = 6378.1366
-	firstLatitude := first.Latitude * math.Pi / 180
-	secondLatitude := second.Latitude * math.Pi / 180
-	deltaLatitude := secondLatitude - firstLatitude
-	deltaLongitude := math.Remainder(second.Longitude-first.Longitude, 360) * math.Pi / 180
-	sineLatitude := math.Sin(deltaLatitude / 2)
-	sineLongitude := math.Sin(deltaLongitude / 2)
-	a := sineLatitude*sineLatitude + math.Cos(firstLatitude)*math.Cos(secondLatitude)*sineLongitude*sineLongitude
-	return 2 * radiusKM * math.Atan2(math.Sqrt(math.Max(0, a)), math.Sqrt(math.Max(0, 1-a)))
-}
-
 func reverseOccultationGeoPoints(points []geodata.GeoPoint) {
 	for left, right := 0, len(points)-1; left < right; left, right = left+1, right-1 {
 		points[left], points[right] = points[right], points[left]