feat: 引入可切换星历模型并扩展天象观测链路

- 新增半解析、旧模型、自定义与多源堆叠星历实例，提供 Context、Instance、SPK 读取及状态与视位置计算
- 统一太阳、月球和行星实例接口，扩展黄经穿越、留、相位、最近角距、偕日可见、任意高度升落、轨道节点及凌日等天象查询
- 完善日月食、月掩与凌日的月缘剖面、有限盘面接触、站心修正、局地可见性、全球路径和地图输出
- 新增 SVG、GeoJSON、KML 天象输出及凌日、月掩和月缘地形相关缓存与几何求解
- 新增恒星星表导入与查询，支持 CSV、Hipparcos、BSC5、Stellarium 等格式及名称、交叉标识、锥面检索和星等过滤
- 补充 IAU 2006、地球定向、折射消光、大气观测、轨道传播及半解析行星/月球数据支持
- 将默认未来民用时标切换为 TimeScaleLeapHour，更新 2027–2400 农历速查表、中文日期解析和时区边界处理
- 增加事件基线、跨模型回归、几何边界、月缘地形和输出契约测试，完善中英文手册、示例资源、NOTICE 与忽略规则

geojson/regulus_20261007_regression_test.go

@@ -0,0 +1,70 @@
+package geojson_test
+
+import (
+	"encoding/json"
+	"testing"
+	"time"
+
+	"b612.me/astro/basic"
+	"b612.me/astro/geojson"
+	"b612.me/astro/moon"
+)
+
+func TestMarshalStarOccultationRegulus20261007UsesAnalyticVisibleEnvelope(t *testing.T) {
+	if err := basic.LoadStarData(); err != nil {
+		t.Fatal(err)
+	}
+	starData, err := basic.StarDataByHR(3982)
+	if err != nil {
+		t.Fatal(err)
+	}
+	star, err := moon.StarCoordinateFromStarData(starData)
+	if err != nil {
+		t.Fatal(err)
+	}
+	start := time.Date(2026, time.October, 7, 0, 0, 0, 0, time.UTC)
+	paths, err := moon.FindStarOccultationPaths(start, start.Add(24*time.Hour), star, moon.OccultationPathOptions{})
+	if err != nil || len(paths) != 1 {
+		t.Fatalf("FindStarOccultationPaths() paths=%d err=%v, want one", len(paths), err)
+	}
+	path := paths[0]
+	if len(path.Footprints) == 0 || len(path.BandFootprints) != 0 {
+		t.Fatalf("dense path footprints=%d bandFootprints=%d, want dense mode", len(path.Footprints), len(path.BandFootprints))
+	}
+	data, err := geojson.MarshalStarOccultation(path)
+	if err != nil {
+		t.Fatalf("MarshalStarOccultation: %v", err)
+	}
+	collection := decodeCollection(t, data)
+	band := featureWithRole(t, collection, "occultation-band")
+	if authoritative, ok := band.Properties["static_band_authoritative"].(bool); !ok || !authoritative {
+		t.Fatalf("occultation-band source=%v authoritative=%v, want analytic authoritative boundary",
+			band.Properties["source"], band.Properties["static_band_authoritative"])
+	}
+	if source := band.Properties["source"]; source != "visible-footprint-sweep" {
+		t.Fatalf("occultation-band source=%v, want visible-footprint-sweep", source)
+	}
+	assertClosedMultiPolygon(t, band)
+	if rings := geoJSONMultiPolygonOuterRings(t, band); len(rings) != 1 {
+		t.Fatalf("occultation-band polygons=%d, want one continuous visible band", len(rings))
+	}
+	assertOccultationBandMaximumEdge(t, band, 45)
+	for _, feature := range featuresWithRole(collection, "visibility-boundary") {
+		var lines [][][]float64
+		if err := json.Unmarshal(feature.Geometry.Coordinates, &lines); err != nil {
+			t.Fatalf("decode visibility-boundary: %v", err)
+		}
+		for lineIndex, line := range lines {
+			for pointIndex, point := range line {
+				if len(point) < 2 || !geometryContainsPointWithinKM(t, band.Geometry, point[0], point[1], 2) {
+					t.Fatalf("visibility-boundary line %d point %d lies outside visible band at %.6f, %.6f", lineIndex, pointIndex, point[0], point[1])
+				}
+			}
+		}
+	}
+	for index, point := range path.CenterLine {
+		if !geometryContainsPoint(t, band.Geometry, point.Longitude, point.Latitude) {
+			t.Fatalf("center-line sample %d lies outside visible band at %.6f, %.6f", index, point.Longitude, point.Latitude)
+		}
+	}
+}