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

eclipse/svg/data_source_test.go

@@ -17,6 +17,7 @@ func TestEclipseMapDataSourcesUseDocumentedVocabulary(t *testing.T) {
 		"besselian-critical-envelope", "paired-limit-chords", "sampled-open-sweep",
 		"central-path-limits", "penumbral-outlines", "central-shadow-outlines",
 		"p1-p4-visibility-regions", "p1-p4-horizon-boundaries",
+		"c1-c4-visibility-regions", "c1-c4-horizon-boundaries", "transit-contact-isochrones",
 	}
 	if len(documented) != len(eclipseMapDataSources) {
 		t.Fatalf("vocabulary has %d entries, want %d", len(eclipseMapDataSources), len(documented))
@@ -51,6 +52,13 @@ func TestEclipseMapDataSourcesUseDocumentedVocabulary(t *testing.T) {
 		t.Fatal("missing 2026-03-03 lunar map")
 	}
 
+	if rendered, ok := TransitMapSVG(TransitVenus, time.Date(2012, time.June, 6, 0, 0, 0, 0, time.UTC),
+		TransitMapSVGOptions{Location: time.UTC, Isochrones: TransitIsochroneExternal, IsochroneStep: 10 * time.Minute}); ok {
+		charts["2012-06-06 venus transit"] = rendered
+	} else {
+		t.Fatal("missing 2012-06-06 transit map")
+	}
+
 	seen := map[string]bool{}
 	for name, chart := range charts {
 		for _, match := range eclipseMapDataSourcePattern.FindAllStringSubmatch(chart, -1) {
@@ -73,6 +81,9 @@ func TestEclipseMapDataSourcesUseDocumentedVocabulary(t *testing.T) {
 		eclipseMapSourceCentralShadowOutlines,
 		eclipseMapSourceLunarVisibilityRegions,
 		eclipseMapSourceLunarHorizonBoundaries,
+		eclipseMapSourceTransitVisibilityRegions,
+		eclipseMapSourceTransitHorizonBoundaries,
+		eclipseMapSourceTransitContactIsochrones,
 	} {
 		if !seen[source] {
 			t.Fatalf("main layer source %q carries no data-source marker", source)