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

coord/research_test.go

@@ -0,0 +1,105 @@
+package coord
+
+import (
+	"math"
+	"testing"
+	"time"
+)
+
+func TestObliquityDrivenCoordinateConversions(t *testing.T) {
+	date := time.Date(2026, 4, 27, 10, 30, 45, 0, time.FixedZone("CST", 8*3600))
+	lon := 139.686111
+	lat := 4.875278
+	obliquity := EclipticObliquity(date, true)
+
+	got := EclipticToEquatorialByObliquity(lon, lat, obliquity)
+	want := EclipticToEquatorial(date, lon, lat)
+	assertClose(t, "manual obliquity ra", got.RA, want.RA, 1e-12)
+	assertClose(t, "manual obliquity dec", got.Dec, want.Dec, 1e-12)
+
+	back := EquatorialToEclipticByObliquity(got.RA, got.Dec, obliquity)
+	assertClose(t, "manual obliquity lon", back.Lon, lon, 1e-10)
+	assertClose(t, "manual obliquity lat", back.Lat, lat, 1e-10)
+}
+
+func TestHourAngleDrivenHorizontalConversions(t *testing.T) {
+	date := time.Date(2026, 4, 27, 2, 30, 45, 0, time.UTC)
+	ra := 101.28715533
+	dec := -16.71611586
+	observerLon := 115.0
+	observerLat := 40.0
+	hourAngle := HourAngle(date, ra, observerLon)
+
+	got := HourAngleDeclinationToHorizontal(hourAngle, dec, observerLat)
+	want := EquatorialToHorizontal(date, ra, dec, observerLon, observerLat)
+	assertClose(t, "manual hour angle azimuth", got.Azimuth, want.Azimuth, 1e-12)
+	assertClose(t, "manual hour angle altitude", got.Altitude, want.Altitude, 1e-12)
+	assertClose(t, "manual hour angle zenith", got.Zenith, want.Zenith, 1e-12)
+	assertClose(t, "manual hour angle value", got.HourAngle, want.HourAngle, 1e-12)
+
+	roundTripHourAngle, roundTripDeclination := HorizontalToHourAngleDeclination(got.Azimuth, got.Altitude, observerLat)
+	assertClose(t, "round trip hour angle", roundTripHourAngle, normalize360(hourAngle), 1e-10)
+	assertClose(t, "round trip declination", roundTripDeclination, dec, 1e-10)
+}
+
+func TestLocalSiderealTimeDrivenHorizontalConversions(t *testing.T) {
+	date := time.Date(2026, 4, 27, 2, 30, 45, 0, time.UTC)
+	ra := 101.28715533
+	dec := -16.71611586
+	observerLon := 115.0
+	observerLat := 40.0
+	localSiderealTimeHours := math.Mod(ApparentSiderealTime(date)+observerLon/15, 24)
+	if localSiderealTimeHours < 0 {
+		localSiderealTimeHours += 24
+	}
+
+	got := EquatorialToHorizontalByLocalSiderealTime(localSiderealTimeHours, ra, dec, observerLat)
+	want := EquatorialToHorizontal(date, ra, dec, observerLon, observerLat)
+	assertClose(t, "LST azimuth", got.Azimuth, want.Azimuth, 1e-12)
+	assertClose(t, "LST altitude", got.Altitude, want.Altitude, 1e-12)
+	assertClose(t, "LST zenith", got.Zenith, want.Zenith, 1e-12)
+	assertClose(t, "LST hour angle", got.HourAngle, want.HourAngle, 1e-12)
+
+	back := HorizontalToEquatorialByLocalSiderealTime(localSiderealTimeHours, got.Azimuth, got.Altitude, observerLat)
+	assertClose(t, "LST round trip ra", back.RA, ra, 1e-10)
+	assertClose(t, "LST round trip dec", back.Dec, dec, 1e-10)
+}
+
+func TestGalacticCoordinateConversions(t *testing.T) {
+	galacticCenter := EquatorialToGalactic(266.4051, -28.936175)
+	assertClose(t, "galactic center lon", galacticCenter.Lon, 0, 5e-4)
+	assertClose(t, "galactic center lat", galacticCenter.Lat, 0, 5e-4)
+
+	pole := GalacticToEquatorial(0, 90)
+	assertClose(t, "north galactic pole ra", pole.RA, 192.85948, 1e-5)
+	assertClose(t, "north galactic pole dec", pole.Dec, 27.12825, 1e-5)
+
+	sample := EquatorialToGalactic(83.6331, 22.0145)
+	back := GalacticToEquatorial(sample.Lon, sample.Lat)
+	assertClose(t, "galactic round trip ra", back.RA, 83.6331, 1e-10)
+	assertClose(t, "galactic round trip dec", back.Dec, 22.0145, 1e-10)
+}
+
+func TestHorizontalRoundTripAcrossQuadrants(t *testing.T) {
+	samples := []struct {
+		hourAngle   float64
+		declination float64
+		latitude    float64
+	}{
+		{15, 20, 35},
+		{95, -10, 52},
+		{210, 45, -20},
+		{315, -35, 10},
+	}
+
+	for _, sample := range samples {
+		hz := HourAngleDeclinationToHorizontal(sample.hourAngle, sample.declination, sample.latitude)
+		hourAngle, declination := HorizontalToHourAngleDeclination(hz.Azimuth, hz.Altitude, sample.latitude)
+		if math.Abs(hourAngle-normalize360(sample.hourAngle)) > 1e-10 {
+			t.Fatalf("hour angle round trip mismatch: got %.15f want %.15f", hourAngle, normalize360(sample.hourAngle))
+		}
+		if math.Abs(declination-sample.declination) > 1e-10 {
+			t.Fatalf("declination round trip mismatch: got %.15f want %.15f", declination, sample.declination)
+		}
+	}
+}