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_envelope_containment_test.go

@@ -0,0 +1,51 @@
+package basic
+
+import (
+	"fmt"
+	"testing"
+)
+
+func TestSolarEclipseAnnularEnvelopeContainsShadow(t *testing.T) {
+	for _, date := range [][3]int{{4005, 4, 22}, {4329, 6, 12}} {
+		t.Run(fmt.Sprintf("%04d-%02d-%02d", date[0], date[1], date[2]), func(t *testing.T) {
+			result := SolarEclipsePartialFootprints(JDECalc(date[0], date[1], float64(date[2])), SolarEclipsePartialFootprintOptions{
+				StepDays: 2.0 / 1440, BoundaryPoints: 96, CentralShadowStepDays: 1.0 / 1440,
+			})
+			if len(result.CentralBandSegments) == 0 {
+				t.Fatal("missing central envelope")
+			}
+			// The static horizon caps describe visible local greatest. Shadow
+			// slices at the limb also include sites whose greatest is below the
+			// horizon; use fully risen samples to audit the two side envelopes.
+			var visible []SolarEclipsePartialFootprint
+			for _, footprint := range result.CentralShadowFootprints {
+				for _, boundary := range footprint.Boundaries {
+					for _, point := range boundary {
+						if point.SunAltitude > 0.5 {
+							visible = append(visible, SolarEclipsePartialFootprint{Boundaries: [][]SolarEclipsePathPoint{{point}}})
+						}
+					}
+				}
+			}
+			if len(visible) == 0 {
+				t.Fatal("missing visible shadow witnesses")
+			}
+			miss := solarEclipseBandFootprintMissDistanceKM(result.CentralBandSegments, visible)
+			if miss > 2 {
+				t.Fatalf("central envelope excludes instantaneous shadow by %.3f km", miss)
+			}
+		})
+	}
+}
+
+func BenchmarkSolarEclipseCentralEnvelopePath(b *testing.B) {
+	for _, date := range [][3]int{{4005, 4, 22}, {4329, 6, 12}, {2024, 4, 8}} {
+		b.Run(fmt.Sprint(date), func(b *testing.B) {
+			seed := JDECalc(date[0], date[1], float64(date[2]))
+			b.ReportAllocs()
+			for i := 0; i < b.N; i++ {
+				SolarEclipseCentralPath(seed, SolarEclipsePathOptions{StepDays: 2.0 / 1440, TargetSpacingKM: 150})
+			}
+		})
+	}
+}