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

calendar/chineseSanGuo.go

@@ -1,7 +1,7 @@
 package calendar
 
 // 蜀汉朔日表
-func shuCals() map[int]uint32 {
+var shuCals = memoUint32Map(func() map[int]uint32 {
 	return map[int]uint32{
 		237: 2862623744,
 		238: 3042255104,
@@ -31,44 +31,50 @@ func shuCals() map[int]uint32 {
 		262: 2862622208,
 		263: 3578927872,
 	}
-}
+})
 
-func shuEras() []Era {
+var shuEras = memoEras(func() []Era {
 	return []Era{
 		{
 			Year:              264,
 			Emperor:           "魏元帝",
 			OtherNianHaoStart: "咸熙",
+			Dynasty:           "魏",
 		},
 		{
 			Year:              263,
 			Emperor:           "蜀后主",
 			OtherNianHaoStart: "炎兴",
+			Dynasty:           "蜀",
 		},
 		{
 			Year:    258,
 			Emperor: "蜀后主",
 			Nianhao: "景耀",
+			Dynasty: "蜀",
 		},
 		{
 			Year:    238,
 			Emperor: "蜀后主",
 			Nianhao: "延熙",
+			Dynasty: "蜀",
 		},
 		{
 			Year:              223,
 			Emperor:           "蜀后主",
 			OtherNianHaoStart: "建兴",
+			Dynasty:           "蜀",
 		},
 		{
 			Year:    221,
 			Emperor: "蜀昭烈帝",
 			Nianhao: "章武",
+			Dynasty: "蜀",
 		},
 	}
-}
+})
 
-func shuEraMap() map[string][][]int {
+var shuEraMap = memoEraMap(func() map[string][][]int {
 	return map[string][][]int{
 		"炎兴": [][]int{{263, 263}},
 		"景耀": [][]int{{258, 263}},
@@ -76,9 +82,9 @@ func shuEraMap() map[string][][]int {
 		"建兴": [][]int{{223, 237}},
 		"章武": [][]int{{221, 223}},
 	}
-}
+})
 
-func wuCals() map[int]uint32 {
+var wuCals = memoUint32Map(func() map[int]uint32 {
 	return map[int]uint32{
 		223: 1432367360,
 		224: 2862622208,
@@ -139,9 +145,9 @@ func wuCals() map[int]uint32 {
 		279: 1454087680,
 		280: 1436561664,
 	}
-}
+})
 
-func wuEraMap() map[string][][]int {
+var wuEraMap = memoEraMap(func() map[string][][]int {
 	return map[string][][]int{
 		"天玺": [][]int{{276, 276}},
 		"天册": [][]int{{275, 276}},
@@ -160,9 +166,9 @@ func wuEraMap() map[string][][]int {
 		"黄龙": [][]int{{229, 231}},
 		"黄武": [][]int{{222, 229}},
 	}
-}
+})
 
-func wuEras() []Era {
+var wuEras = memoEras(func() []Era {
 	return []Era{
 		{
 			Year:    277,
@@ -267,39 +273,47 @@ func wuEras() []Era {
 			Dynasty: "吴",
 		},
 	}
-}
+})
 
 func innerSolarToLunarSanGuo(date Time) Time {
 	year := date.solarTime.Year()
 	month := int(date.solarTime.Month())
 	day := date.solarTime.Day()
+	// 农历年早于年号表首年（如 221 年初尚属农历 220 年）时 eras 为空，
+	// 该候选与其它候选日期完全相同且无朝代，不再追加。
 	if year >= 221 && year <= 263 {
 		lyear, lmonth, ganzhiMonth, lday, isLeap, ldesc := rapidLunarHan2Qing(year, month, day, 0, shuCals)
-		date.lunars = append(date.lunars, LunarTime{
-			solarDate:   date.solarTime,
-			year:        lyear,
-			month:       lmonth,
-			day:         lday,
-			leap:        isLeap,
-			desc:        ldesc,
-			comment:     "",
-			ganzhiMonth: ganzhiMonth,
-			eras:        innerEras(lyear, shuEras),
-		})
+		eras := innerEras(lyear, shuEras)
+		if len(eras) > 0 {
+			date.lunars = append(date.lunars, LunarTime{
+				solarDate:   date.solarTime,
+				year:        lyear,
+				month:       lmonth,
+				day:         lday,
+				leap:        isLeap,
+				desc:        ldesc,
+				comment:     "",
+				ganzhiMonth: ganzhiMonth,
+				eras:        eras,
+			})
+		}
 	}
 	if year >= 222 && year <= 280 {
 		lyear, lmonth, ganzhiMonth, lday, isLeap, ldesc := rapidLunarHan2Qing(year, month, day, 0, wuCals)
-		date.lunars = append(date.lunars, LunarTime{
-			solarDate:   date.solarTime,
-			year:        lyear,
-			month:       lmonth,
-			day:         lday,
-			leap:        isLeap,
-			desc:        ldesc,
-			ganzhiMonth: ganzhiMonth,
-			comment:     "",
-			eras:        innerEras(lyear, wuEras),
-		})
+		eras := innerEras(lyear, wuEras)
+		if len(eras) > 0 {
+			date.lunars = append(date.lunars, LunarTime{
+				solarDate:   date.solarTime,
+				year:        lyear,
+				month:       lmonth,
+				day:         lday,
+				leap:        isLeap,
+				desc:        ldesc,
+				ganzhiMonth: ganzhiMonth,
+				comment:     "",
+				eras:        eras,
+			})
+		}
 	}
 	return date
 }