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_29020726_regression_test.go

@@ -0,0 +1,49 @@
+package geojson_test
+
+import (
+	"testing"
+	"time"
+
+	"b612.me/astro/eclipse"
+	"b612.me/astro/geojson"
+)
+
+func TestMarshalSolarEclipse29020726DoesNotFillNighttimeCanada(t *testing.T) {
+	date := time.Date(2902, time.July, 26, 0, 0, 0, 0, time.UTC)
+	partial, ok := eclipse.SolarEclipsePartialFootprints(date, eclipse.SolarEclipsePartialFootprintOptions{
+		Step: 2 * time.Minute, BoundaryPoints: 96, CentralShadowStep: 2 * time.Minute,
+		MagnitudeValues: []float64{0.2, 0.4, 0.6, 0.8, 1.0},
+	})
+	if !ok {
+		t.Fatal("expected solar eclipse footprints")
+	}
+	data, err := geojson.MarshalSolarEclipse(partial, nil)
+	if err != nil {
+		t.Fatalf("MarshalSolarEclipse: %v", err)
+	}
+	band := featureWithRole(t, decodeCollection(t, data), "partial-band")
+	if band.Geometry.Type != "MultiPolygon" {
+		t.Fatalf("partial-band geometry=%q, want MultiPolygon", band.Geometry.Type)
+	}
+	for _, site := range []struct {
+		name       string
+		longitude  float64
+		latitude   float64
+		wantInside bool
+	}{
+		{name: "Edmonton", longitude: -113.4909, latitude: 53.5461},
+		{name: "Churchill", longitude: -94.1650, latitude: 58.7684},
+		{name: "Iqaluit", longitude: -68.5170, latitude: 63.7467},
+		{name: "Resolute", longitude: -94.8297, latitude: 74.6973, wantInside: true},
+		{name: "Alert", longitude: -62.3481, latitude: 82.5018, wantInside: true},
+		{name: "Bering east of envelope", longitude: 179, latitude: 65},
+		{name: "Bering inside excluded pocket", longitude: 175, latitude: 65},
+		{name: "Bering west of envelope", longitude: 170, latitude: 65, wantInside: true},
+		{name: "Bering west world", longitude: -179, latitude: 65},
+		{name: "Arctic east world", longitude: 179.9, latitude: 80, wantInside: true},
+	} {
+		if got := geometryContainsPoint(t, band.Geometry, site.longitude, site.latitude); got != site.wantInside {
+			t.Errorf("partial-band contains %s=%v, want %v", site.name, got, site.wantInside)
+		}
+	}
+}