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/doc.go

@@ -1,4 +1,4 @@
-// Package svg 生成日食与月食的 SVG 图件。
+// Package svg 生成日食、月食与水星、金星凌日的 SVG 图件。
 //
 // 可降级的图层用 data-source 标注实际几何来源，取值词表如下；没有降级分支的图层不带该属性。
 //
@@ -16,27 +16,33 @@
 //	central-shadow-outlines      瞬时本影、反本影轮廓
 //	p1-p4-visibility-regions     月食可见性分区
 //	p1-p4-horizon-boundaries     月食 P1、P4 地平边界
+//	c1-c4-visibility-regions     凌日可见性分区
+//	c1-c4-horizon-boundaries     凌日 C1、C4 视地平边界
+//	transit-contact-isochrones   凌日站心接触等时线
 //
-// Package svg renders solar- and lunar-eclipse SVG charts. Degradable layers tag the geometry
+// Package svg renders solar-eclipse, lunar-eclipse and Mercury/Venus transit SVG charts. Degradable layers tag the geometry
 // source they actually used in data-source, using exactly the values above.
 package svg
 
 // data-source 词表，见包注释。
 const (
-	eclipseMapSourcePartialBandUnion       = "partial-band-union"
-	eclipseMapSourceSampledFootprintSweep  = "sampled-footprint-sweep"
-	eclipseMapSourcePartialBandContours    = "partial-band-contours"
-	eclipseMapSourceRiseSetPhaseLines      = "rise-set-phase-lines"
-	eclipseMapSourceMagnitudeContours      = "magnitude-contours"
-	eclipseMapSourceGreatestTimeIsochrones = "greatest-time-isochrones"
-	eclipseMapSourceBesselianEnvelope      = "besselian-critical-envelope"
-	eclipseMapSourcePairedLimitChords      = "paired-limit-chords"
-	eclipseMapSourceSampledOpenSweep       = "sampled-open-sweep"
-	eclipseMapSourceCentralPathLimits      = "central-path-limits"
-	eclipseMapSourcePenumbralOutlines      = "penumbral-outlines"
-	eclipseMapSourceCentralShadowOutlines  = "central-shadow-outlines"
-	eclipseMapSourceLunarVisibilityRegions = "p1-p4-visibility-regions"
-	eclipseMapSourceLunarHorizonBoundaries = "p1-p4-horizon-boundaries"
+	eclipseMapSourcePartialBandUnion         = "partial-band-union"
+	eclipseMapSourceSampledFootprintSweep    = "sampled-footprint-sweep"
+	eclipseMapSourcePartialBandContours      = "partial-band-contours"
+	eclipseMapSourceRiseSetPhaseLines        = "rise-set-phase-lines"
+	eclipseMapSourceMagnitudeContours        = "magnitude-contours"
+	eclipseMapSourceGreatestTimeIsochrones   = "greatest-time-isochrones"
+	eclipseMapSourceBesselianEnvelope        = "besselian-critical-envelope"
+	eclipseMapSourcePairedLimitChords        = "paired-limit-chords"
+	eclipseMapSourceSampledOpenSweep         = "sampled-open-sweep"
+	eclipseMapSourceCentralPathLimits        = "central-path-limits"
+	eclipseMapSourcePenumbralOutlines        = "penumbral-outlines"
+	eclipseMapSourceCentralShadowOutlines    = "central-shadow-outlines"
+	eclipseMapSourceLunarVisibilityRegions   = "p1-p4-visibility-regions"
+	eclipseMapSourceLunarHorizonBoundaries   = "p1-p4-horizon-boundaries"
+	eclipseMapSourceTransitVisibilityRegions = "c1-c4-visibility-regions"
+	eclipseMapSourceTransitHorizonBoundaries = "c1-c4-horizon-boundaries"
+	eclipseMapSourceTransitContactIsochrones = "transit-contact-isochrones"
 )
 
 // eclipseMapDataSources 是全部合法取值，测试用它封闭词表。
@@ -55,4 +61,7 @@ var eclipseMapDataSources = []string{
 	eclipseMapSourceCentralShadowOutlines,
 	eclipseMapSourceLunarVisibilityRegions,
 	eclipseMapSourceLunarHorizonBoundaries,
+	eclipseMapSourceTransitVisibilityRegions,
+	eclipseMapSourceTransitHorizonBoundaries,
+	eclipseMapSourceTransitContactIsochrones,
 }