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

basic/solar_eclipse_total_envelope_test.go

@@ -0,0 +1,62 @@
+package basic
+
+import (
+	"fmt"
+	"math"
+	"testing"
+)
+
+func TestSolarEclipseTotalEnvelopeHorizonEndpoints(t *testing.T) {
+	for _, date := range [][3]int{
+		{2003, 11, 23}, {2021, 12, 4}, {2039, 12, 15},
+		{2008, 8, 1}, {2024, 4, 8}, {2026, 8, 12},
+	} {
+		t.Run(fmt.Sprintf("%04d-%02d-%02d", date[0], date[1], date[2]), func(t *testing.T) {
+			seed := JDECalc(date[0], date[1], float64(date[2]))
+			result := SolarEclipsePartialFootprints(seed, SolarEclipsePartialFootprintOptions{
+				StepDays: 2.0 / 1440, BoundaryPoints: 96, MagnitudeValues: []float64{1},
+			})
+			if result.Eclipse.Type != SolarEclipseTotal || len(result.CentralBandSegments) != 1 ||
+				len(result.CentralBandHorizonClosures) != 2 {
+				t.Fatalf("type=%s rings=%d closures=%d, want total with a continuous closed envelope",
+					result.Eclipse.Type, len(result.CentralBandSegments), len(result.CentralBandHorizonClosures))
+			}
+			if len(result.MagnitudeContours) != 1 || len(result.MagnitudeContours[0].Segments) != 2 {
+				t.Fatal("missing totality branches")
+			}
+			ring := result.CentralBandSegments[0]
+			if len(ring) < 4 || ring[0] != ring[len(ring)-1] {
+				t.Fatal("totality envelope is not closed")
+			}
+			solver := newSolarEclipseSolver(CalcMoonSHByJDE(seed, 0), SolarEclipseModelNASABulletinSplitK)
+			for i, point := range ring {
+				if i > 0 && solarEclipsePathDistanceKM(ring[i-1], point) > solarEclipseTotalEnvelopeTargetSpacingKM+1e-6 {
+					t.Fatalf("edge %d exceeds spacing limit", i)
+				}
+				if solarEclipseCentralEnvelopePointOnHorizonClosure(point, result.CentralBandHorizonClosures) {
+					continue
+				}
+				residual, ok := solver.magnitudeHorizonResidual(point.JDE, point.Longitude, point.Latitude, 1)
+				if !ok || math.Abs(residual[0]) > 1e-7 || math.Abs(residual[1]) > 1e-8 || point.SunAltitude < -1e-5 {
+					t.Fatalf("point %d is not on visible totality envelope: %v altitude=%g", i, residual, point.SunAltitude)
+				}
+			}
+			for _, branch := range result.MagnitudeContours[0].Segments {
+				for _, endpoint := range []SolarEclipsePathPoint{branch[0], branch[len(branch)-1]} {
+					if !solarEclipseCentralEnvelopePointOnHorizonClosure(endpoint, result.CentralBandHorizonClosures) {
+						t.Fatal("totality endpoint is not shared with a horizon closure")
+					}
+				}
+			}
+		})
+	}
+}
+
+func BenchmarkSolarEclipsePolarTotalBand(b *testing.B) {
+	seed := JDECalc(2003, 11, 23)
+	for i := 0; i < b.N; i++ {
+		SolarEclipsePartialFootprints(seed, SolarEclipsePartialFootprintOptions{
+			StepDays: 2.0 / 1440, BoundaryPoints: 96, DisableRiseSetCurves: true,
+		})
+	}
+}