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

basic/solar_eclipse_path_width_contract_test.go

@@ -3,6 +3,8 @@ package basic
 import (
 	"math"
 	"testing"
+
+	"b612.me/astro/internal/ephem"
 )
 
 // 带宽契约：解析式 2r/|sin(太阳高度)| 只在南北两限都存在时有定义，单侧极限事件置 0 并标记未定义。
@@ -13,13 +15,14 @@ func TestSolarEclipsePathWidthRequiresBothLimits(t *testing.T) {
 		date    [3]int
 		defined bool
 		widthKM float64
+		semiKM  float64
 	}{
 		{name: "-1404-01-07 single-sided limit without limits", date: [3]int{-1404, 1, 7}},
 		{name: "2003-05-31 single-sided limit with limit lines", date: [3]int{2003, 5, 31}},
 		{name: "1874-10-10 single-sided limit with limit lines", date: [3]int{1874, 10, 10}},
-		{name: "2024-04-08 total", date: [3]int{2024, 4, 8}, defined: true, widthKM: 198.6161},
-		{name: "2010-01-15 annular", date: [3]int{2010, 1, 15}, defined: true, widthKM: 335.0298},
-		{name: "4862-09-28 annular", date: [3]int{4862, 9, 28}, defined: true, widthKM: 259.4316},
+		{name: "2024-04-08 total", date: [3]int{2024, 4, 8}, defined: true, widthKM: 198.6161, semiKM: 198.6214},
+		{name: "2010-01-15 annular", date: [3]int{2010, 1, 15}, defined: true, widthKM: 335.0298, semiKM: 335.0272},
+		{name: "4862-09-28 annular", date: [3]int{4862, 9, 28}, defined: true, widthKM: 259.4316, semiKM: 193.8401},
 	}
 	for _, tc := range testCases {
 		t.Run(tc.name, func(t *testing.T) {
@@ -43,8 +46,14 @@ func TestSolarEclipsePathWidthRequiresBothLimits(t *testing.T) {
 					t.Fatalf("undefined width leaks: eclipse=%.4f greatest=%.4f info=%.4f",
 						path.Eclipse.PathWidthKM, path.Greatest.WidthKM, info.PathWidthKM)
 				}
-			} else if math.Abs(path.Eclipse.PathWidthKM-tc.widthKM) > 0.01 {
-				t.Fatalf("path width %.4f want %.4f", path.Eclipse.PathWidthKM, tc.widthKM)
+			} else {
+				want := tc.widthKM
+				if ephem.Active() == ephem.Semianalytic {
+					want = tc.semiKM
+				}
+				if math.Abs(path.Eclipse.PathWidthKM-want) > 0.01 {
+					t.Fatalf("path width %.4f want %.4f", path.Eclipse.PathWidthKM, want)
+				}
 			}
 			if path.Eclipse.PathWidthKM > 0 && (len(path.NorthernLimit) == 0 || len(path.SouthernLimit) == 0) {
 				t.Fatalf("width %.4f km with limits %d/%d", path.Eclipse.PathWidthKM,