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

internal/limbnote/limbnote.go

@@ -0,0 +1,96 @@
+// Package limbnote 生成出图时写入图注的月面口径声明。
+package limbnote
+
+import "strings"
+
+const english = "en"
+
+// Contacts 接触时刻所用月面口径的短标签，保持站心图页脚平衡 / short tag for the contact-time limb convention.
+func Contacts(applied bool, language string) string {
+	if applied {
+		if language == english {
+			return "Limb profile."
+		}
+		return "月缘剖面。"
+	}
+	if language == english {
+		return "Circular limb."
+	}
+	return "圆月面。"
+}
+
+// Limits 界线所用月面口径；可见域与等时线始终按圆月面 / limb convention for limit tracks only.
+func Limits(applied bool, language string) string {
+	if applied {
+		if language == english {
+			return "Limits use the lunar limb profile (areas and isolines circular)."
+		}
+		return "界线按月缘剖面修正（可见域与等时线仍按圆月面）。"
+	}
+	if language == english {
+		return "Circular lunar limb."
+	}
+	return "月面按圆月面计算。"
+}
+
+// SolarMapLayers 日食全球图各层是否真正按月缘剖面修正 / which global solar map layers the lunar limb actually corrected.
+type SolarMapLayers struct {
+	// GlobalContacts 全球偏食始末与食甚点中心食时长 / global P1/P4 and the central duration at greatest eclipse.
+	GlobalContacts bool
+	// LocalPanel 食甚点站心面板 / the local panel at greatest eclipse.
+	LocalPanel bool
+	// CentralLimits 中心带南北界与带宽 / central-band limits and width.
+	CentralLimits bool
+	// PartialBoundary 偏食可见域外边界 / the outer partial visibility boundary.
+	PartialBoundary bool
+}
+
+// SolarMap 按实际生效的层列出日食全球图的月缘修正，食分线与等时线始终按圆月面 / lists the corrected layers of the global solar map.
+func SolarMap(layers SolarMapLayers, language string) string {
+	type layer struct {
+		applied     bool
+		zh, english string
+	}
+	var names []string
+	for _, item := range []layer{
+		{layers.GlobalContacts, "全球始末", "global contacts"},
+		{layers.LocalPanel, "食甚点站心值", "local values at greatest eclipse"},
+		{layers.CentralLimits, "中心带界线", "central limits"},
+		{layers.PartialBoundary, "可见域边界", "visibility boundary"},
+	} {
+		if !item.applied {
+			continue
+		}
+		if language == english {
+			names = append(names, item.english)
+		} else {
+			names = append(names, item.zh)
+		}
+	}
+	if len(names) == 0 {
+		return Limits(false, language)
+	}
+	if language == english {
+		return "Lunar limb profile applied to " + strings.Join(names, ", ") + " (isolines circular)."
+	}
+	return "按月缘剖面修正" + strings.Join(names, "、") + "（食分线与等时线仍按圆月面）。"
+}
+
+// Join 把月面口径声明接在时标声明之后，二者同占一行 / appends the limb declaration to the time-scale note.
+func Join(scaleNote, limbNote, language string) string {
+	switch {
+	case scaleNote == "":
+		return limbNote
+	case limbNote == "":
+		return scaleNote
+	case strings.HasSuffix(scaleNote, "。") || strings.HasSuffix(scaleNote, "."):
+		if language == english {
+			return scaleNote + " " + limbNote
+		}
+		return scaleNote + limbNote
+	case language == english:
+		return scaleNote + ". " + limbNote
+	default:
+		return scaleNote + "；" + limbNote
+	}
+}