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

semantics_regression_test.go

@@ -189,7 +189,8 @@ func TestObservationZenithMatchesIndependentFormula(t *testing.T) {
 			jde := basic.Date2JD(date)
 			_, loc := date.Zone()
 			timezone := float64(loc) / 3600.0
-			tt := basic.UTC2TT(jde - timezone/24)
+			utcJD := jde - timezone/24
+			tt := basic.UTC2TT(utcJD)
 
 			checks := []struct {
 				name    string
@@ -199,7 +200,7 @@ func TestObservationZenithMatchesIndependentFormula(t *testing.T) {
 			}{
 				{"sun", sunTolerance,
 					sun.Zenith(date, place.lon, place.lat),
-					zenithFromHourAngle(sun.HourAngle(date, place.lon, place.lat), basic.HSunApparentDec(tt), place.lat)},
+					topocentricZenith(sun.HourAngle(date, place.lon, place.lat), basic.HSunApparentRa(tt), basic.HSunApparentDec(tt), basic.EarthAway(tt), place.lat, place.lon, utcJD)},
 				{"moon", moonTolerance,
 					moon.Zenith(date, place.lon, place.lat),
 					zenithFromHourAngle(moon.HourAngle(date, place.lon, place.lat), moon.ApparentDec(date, place.lon, place.lat), place.lat)},
@@ -211,25 +212,25 @@ func TestObservationZenithMatchesIndependentFormula(t *testing.T) {
 					zenithFromHourAngle(star.HourAngle(date, starRa, place.lon), starDec, place.lat)},
 				{"mercury", planetTolerance,
 					mercury.Zenith(date, place.lon, place.lat),
-					zenithFromHourAngle(mercury.HourAngle(date, place.lon), mercury.ApparentDec(date), place.lat)},
+					topocentricZenith(mercury.HourAngle(date, place.lon), mercury.ApparentRa(date), mercury.ApparentDec(date), basic.EarthMercuryAway(tt), place.lat, place.lon, utcJD)},
 				{"venus", planetTolerance,
 					venus.Zenith(date, place.lon, place.lat),
-					zenithFromHourAngle(venus.HourAngle(date, place.lon), venus.ApparentDec(date), place.lat)},
+					topocentricZenith(venus.HourAngle(date, place.lon), venus.ApparentRa(date), venus.ApparentDec(date), basic.EarthVenusAway(tt), place.lat, place.lon, utcJD)},
 				{"mars", planetTolerance,
 					mars.Zenith(date, place.lon, place.lat),
-					zenithFromHourAngle(mars.HourAngle(date, place.lon), mars.ApparentDec(date), place.lat)},
+					topocentricZenith(mars.HourAngle(date, place.lon), mars.ApparentRa(date), mars.ApparentDec(date), basic.EarthMarsAway(tt), place.lat, place.lon, utcJD)},
 				{"jupiter", planetTolerance,
 					jupiter.Zenith(date, place.lon, place.lat),
-					zenithFromHourAngle(jupiter.HourAngle(date, place.lon), jupiter.ApparentDec(date), place.lat)},
+					topocentricZenith(jupiter.HourAngle(date, place.lon), jupiter.ApparentRa(date), jupiter.ApparentDec(date), basic.EarthJupiterAway(tt), place.lat, place.lon, utcJD)},
 				{"saturn", planetTolerance,
 					saturn.Zenith(date, place.lon, place.lat),
-					zenithFromHourAngle(saturn.HourAngle(date, place.lon), saturn.ApparentDec(date), place.lat)},
+					topocentricZenith(saturn.HourAngle(date, place.lon), saturn.ApparentRa(date), saturn.ApparentDec(date), basic.EarthSaturnAway(tt), place.lat, place.lon, utcJD)},
 				{"uranus", planetTolerance,
 					uranus.Zenith(date, place.lon, place.lat),
-					zenithFromHourAngle(uranus.HourAngle(date, place.lon), uranus.ApparentDec(date), place.lat)},
+					topocentricZenith(uranus.HourAngle(date, place.lon), uranus.ApparentRa(date), uranus.ApparentDec(date), basic.EarthUranusAway(tt), place.lat, place.lon, utcJD)},
 				{"neptune", planetTolerance,
 					neptune.Zenith(date, place.lon, place.lat),
-					zenithFromHourAngle(neptune.HourAngle(date, place.lon), neptune.ApparentDec(date), place.lat)},
+					topocentricZenith(neptune.HourAngle(date, place.lon), neptune.ApparentRa(date), neptune.ApparentDec(date), basic.EarthNeptuneAway(tt), place.lat, place.lon, utcJD)},
 			}
 
 			for _, tc := range checks {
@@ -242,6 +243,12 @@ func TestObservationZenithMatchesIndependentFormula(t *testing.T) {
 	}
 }
 
+// topocentricZenith 由地心时角、地心视赤经赤纬与地心距（AU）先做站心视差修正，再独立求天顶距，单位度。
+func topocentricZenith(hourAngle, ra, dec, distanceAU, lat, lon, utcJD float64) float64 {
+	topocentricRA, topocentricDec := basic.TopocentricRaDec(ra, dec, lat, lon, utcJD, distanceAU, 0)
+	return zenithFromHourAngle(hourAngle+ra-topocentricRA, topocentricDec, lat)
+}
+
 // zenithFromHourAngle 由时角与赤纬按 cos z = sinφ·sinδ + cosφ·cosδ·cos H 独立求天顶距，单位度。
 func zenithFromHourAngle(hourAngle, dec, lat float64) float64 {
 	rad := math.Pi / 180