feat: 完善日月食与月掩几何链路并扩展历法接口

- 新增日月食中心带、偏食带、阴影足迹、等时线、食分线及升落边界计算，支持极区与混合食拓扑
- 新增日食单时刻阴影求解器、站心状态查询、批量采样和 ΔT 覆盖接口
- 重构恒星与行星月掩路径，补充有限盘面接触、站心修正、掩带宽度、极区投影及升落边界
- 扩展 SVG 与 GeoJSON 输出，支持详细面板、全球/极区/地球投影、边界闭合、时间标记和拓扑签名
- 扩展日月食候选搜索、局地搜索、沙罗序列预计算与范围外推，补充系列锚点和成员一致性校验
- 补齐古历纪年、儒略历独有闰日、多公历候选、历法改革跨日及精确日期运算接口
- 优化 ΔT、章动、恒星时、月球地平线、事件根搜索和本地星历缓存，降低重复计算开销并提升边界稳定

geojson/solar_partial_envelope_regression_test.go

@@ -0,0 +1,52 @@
+package geojson_test
+
+import (
+	"testing"
+	"time"
+
+	"b612.me/astro/eclipse"
+	"b612.me/astro/geojson"
+	"b612.me/astro/internal/geodata"
+)
+
+func TestSolarPartialEnvelopeCoversHorizonCurves(t *testing.T) {
+	for _, date := range []time.Time{
+		time.Date(43, 3, 29, 0, 0, 0, 0, time.UTC),
+		time.Date(1848, 9, 27, 0, 0, 0, 0, time.UTC),
+		time.Date(2023, 4, 20, 0, 0, 0, 0, time.UTC),
+		time.Date(2025, 3, 29, 0, 0, 0, 0, time.UTC),
+	} {
+		t.Run(date.Format("2006-01-02"), func(t *testing.T) {
+			path, ok := eclipse.SolarEclipsePartialFootprints(date, eclipse.SolarEclipsePartialFootprintOptions{
+				Step: 5 * time.Minute, BoundaryPoints: 96, CentralShadowStep: 5 * time.Minute, RiseSetStep: 2 * time.Minute,
+			})
+			if !ok {
+				t.Fatal("missing eclipse")
+			}
+			data, err := geojson.MarshalSolarEclipse(path, nil)
+			if err != nil {
+				t.Fatal(err)
+			}
+			collection := decodeCollection(t, data)
+			band := featureWithRole(t, collection, "partial-band")
+			if source := band.Properties["source"]; source != "zero-magnitude-envelope+horizon-boundary" {
+				t.Fatalf("incomplete envelope fallback: %v", source)
+			}
+			assertClosedMultiPolygon(t, band)
+			rings := geoJSONMultiPolygonOuterRings(t, band)
+			var lines [][]geodata.GeoPoint
+			for _, curve := range path.RiseSetCurves {
+				for _, segment := range curve.Segments {
+					line := make([]geodata.GeoPoint, len(segment))
+					for i, point := range segment {
+						line[i] = geodata.GeoPoint{Longitude: point.Longitude, Latitude: point.Latitude}
+					}
+					lines = append(lines, line)
+				}
+			}
+			if miss := geodata.SphericalPolygonsPathMissDistanceKM(rings, lines, false); miss > 2 {
+				t.Fatalf("phase curves miss envelope by %.3f km", miss)
+			}
+		})
+	}
+}