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_polar_envelope_test.go

@@ -0,0 +1,84 @@
+package basic
+
+import (
+	"fmt"
+	"math"
+	"testing"
+)
+
+func TestSolarEclipsePolarCentralEnvelope(t *testing.T) {
+	for _, sample := range []struct {
+		year, month, day int
+		direction        RiseSetDirection
+	}{
+		{2061, 10, 13, RiseSetDirectionRise},
+		{2026, 2, 17, RiseSetDirectionSet},
+	} {
+		t.Run(fmt.Sprintf("%04d-%02d-%02d", sample.year, sample.month, sample.day), func(t *testing.T) {
+			seed := JDECalc(sample.year, sample.month, float64(sample.day))
+			result := SolarEclipsePartialFootprints(seed, SolarEclipsePartialFootprintOptions{
+				StepDays: 2.0 / 1440, BoundaryPoints: 96,
+			})
+			if result.Eclipse.Type != SolarEclipseAnnular || len(result.CentralBandSegments) != 1 ||
+				len(result.CentralBandHorizonClosures) != 2 {
+				t.Fatalf("type=%s rings=%d closures=%d, want annular with a continuous closed envelope",
+					result.Eclipse.Type, len(result.CentralBandSegments), len(result.CentralBandHorizonClosures))
+			}
+			solver := newSolarEclipseSolver(CalcMoonSHByJDE(seed, 0), SolarEclipseModelNASABulletinSplitK)
+			for index, closure := range result.CentralBandHorizonClosures {
+				if len(closure) < 2 {
+					t.Fatalf("closure %d has no arc", index)
+				}
+				for _, root := range []SolarEclipsePathPoint{closure[0], closure[len(closure)-1]} {
+					evaluation := solver.magnitudeEvaluationAt(root.JDE)
+					_, key, ok := evaluation.classify(root.Longitude, root.Latitude, true)
+					if !ok || key.direction != sample.direction {
+						t.Fatalf("closure %d direction=%s valid=%v, want %s", index, key.direction, ok, sample.direction)
+					}
+					residual, _, ok := solarEclipseCentralLimitHorizonJacobian(
+						solver, [3]float64{root.Longitude, root.Latitude, root.JDE},
+						solver.magnitudeEvaluationAt,
+					)
+					if !ok || math.Abs(residual[0]) > 1e-9 || math.Abs(residual[1]) > 1e-7 || math.Abs(residual[2]) > 1e-9 {
+						t.Fatalf("closure %d root residual=%v valid=%v", index, residual, ok)
+					}
+				}
+				for pointIndex, point := range closure {
+					matched := false
+					for _, curve := range result.RiseSetCurves {
+						if curve.Phase != RiseSetPhaseGreatest || curve.Direction != sample.direction {
+							continue
+						}
+						for _, segment := range curve.Segments {
+							for _, candidate := range segment {
+								if math.Abs(candidate.JDE-point.JDE) < solarEclipsePathDuplicateTimeDays &&
+									solarEclipsePathDistanceKM(candidate, point) < 0.001 {
+									matched = true
+								}
+							}
+						}
+					}
+					if !matched {
+						t.Fatalf("closure %d point %d is missing from greatest/%s", index, pointIndex, sample.direction)
+					}
+				}
+			}
+			ring := result.CentralBandSegments[0]
+			if len(ring) < 100 || solarEclipsePathDistanceKM(ring[0], ring[len(ring)-1]) > 0.001 {
+				t.Fatal("central envelope is not densely sampled and closed")
+			}
+			for index, point := range ring {
+				if index > 0 && solarEclipsePathDistanceKM(ring[index-1], point) > solarEclipseCentralEnvelopeMaxSpacingKM {
+					t.Fatalf("envelope edge %d exceeds spacing limit", index)
+				}
+				if solarEclipseCentralEnvelopePointOnHorizonClosure(point, result.CentralBandHorizonClosures) {
+					continue
+				}
+				residual, ok := solarEclipseNonCentralBandBoundaryResidualAt(solver.magnitudeEvaluationAt(point.JDE), point.Longitude, point.Latitude)
+				if !ok || math.Abs(residual[0]) > 1e-6 || math.Abs(residual[1]) > solarEclipseNonCentralBandDerivativeTolerance || point.SunAltitude < 0 {
+					t.Fatalf("envelope point %d altitude=%g residual=%v valid=%v", index, point.SunAltitude, residual, ok)
+				}
+			}
+		})
+	}
+}