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_eclipse_total_options_test.go

@@ -0,0 +1,61 @@
+package geojson_test
+
+import (
+	"reflect"
+	"testing"
+	"time"
+
+	"b612.me/astro/eclipse"
+	"b612.me/astro/geojson"
+)
+
+func TestSolarTotalBandIndependentOfMagnitudeLines(t *testing.T) {
+	for _, fixture := range []struct {
+		date     time.Time
+		lon, lat float64
+	}{
+		{time.Date(2026, 8, 12, 0, 0, 0, 0, time.UTC), -5.991755201, 45.070085755},
+		{time.Date(2024, 4, 8, 0, 0, 0, 0, time.UTC), -32.007627414, 49.493804579},
+	} {
+		t.Run(fixture.date.Format("2006-01-02"), func(t *testing.T) {
+			central, ok := eclipse.SolarEclipseCentralPath(fixture.date, eclipse.SolarEclipsePathOptions{Step: time.Minute})
+			if !ok {
+				t.Fatal("missing central path")
+			}
+			local, ok := eclipse.GeometricLocalSolarEclipseOnDate(fixture.date, fixture.lon, fixture.lat, 0)
+			if !ok || local.Type != eclipse.SolarEclipseTotal || !local.VisibleAtGreatest {
+				t.Fatal("invalid totality witness")
+			}
+			var reference [][]eclipse.SolarEclipsePathPoint
+			for _, magnitudes := range [][]float64{nil, {1}} {
+				partial, ok := eclipse.SolarEclipsePartialFootprints(fixture.date, eclipse.SolarEclipsePartialFootprintOptions{
+					Step: 2 * time.Minute, BoundaryPoints: 96, MagnitudeValues: magnitudes,
+				})
+				if !ok || len(partial.CentralBandSegments) == 0 {
+					t.Fatal("missing authoritative totality band")
+				}
+				if reference == nil {
+					reference = partial.CentralBandSegments
+				} else if !reflect.DeepEqual(reference, partial.CentralBandSegments) {
+					t.Fatal("magnitude display option changes totality geometry")
+				}
+				if len(magnitudes) == 0 && len(partial.MagnitudeContours) != 0 {
+					t.Fatal("unrequested magnitude lines")
+				}
+				for _, ring := range partial.CentralBandSegments {
+					assertSolarPathMaximumEdgeKM(t, ring, 250)
+				}
+				for _, path := range []*eclipse.SolarEclipsePath{&central, nil} {
+					data, err := geojson.MarshalSolarEclipse(partial, path)
+					if err != nil {
+						t.Fatal(err)
+					}
+					band := featureWithRole(t, decodeCollection(t, data), "central-band")
+					if !geometryContainsPoint(t, band.Geometry, fixture.lon, fixture.lat) {
+						t.Fatal("totality band omits visible site")
+					}
+				}
+			}
+		})
+	}
+}