feat: 完善时标与天象几何计算并扩展输出接口

- 新增时标、ΔT 模型、质心时间与 UT1 支持
- 改进日月食、月掩、行星事件及路径边界计算
- 完善恒星三维自行与动态距离传播
- 扩展 SVG、GeoJSON、KML 输出与底层距离换算工具
- 整理中英文手册、示例资源及回归测试

astro.go

@@ -1,17 +1,94 @@
-// Package astro 进程级 ΔT 模型的读取、替换与恢复默认：DeltaT、SetDeltaT、DefaultDeltaT。
-// Package astro exposes the process-wide DeltaT model: read the current function, install a custom one, or restore the built-in default.
+// Package astro 提供进程级时标配置与时标换算 / process-wide time-scale configuration and conversions.
 package astro
 
 import "b612.me/astro/basic"
 
+// DeltaT 返回当前的 TT−UT1（ΔT）模型 / the active TT−UT1 (DeltaT) model.
 func DeltaT() func(float64, bool) float64 {
 	return basic.GetDeltaTFn()
 }
 
+// SetDeltaT 替换 ΔT 模型（入参为数值与“该数值是否为儒略日”，为假时是十进制年），传 nil 恢复默认 / replaces the DeltaT model; nil restores the default.
 func SetDeltaT(deltaT func(float64, bool) float64) {
 	basic.SetDeltaTFn(deltaT)
 }
 
+// DefaultDeltaT 返回内置默认 ΔT 模型 / the built-in default DeltaT model.
 func DefaultDeltaT() func(float64, bool) float64 {
 	return basic.DefaultDeltaTv2
 }
+
+// TTMinusUTC 返回当前 TT−UTC 覆盖函数，未设置时为 nil / current TT−UTC override, or nil.
+func TTMinusUTC() func(float64) float64 {
+	return basic.GetTTMinusUTCFn()
+}
+
+// SetTTMinusUTC 替换 TT−UTC 模型，nil 恢复内置表与政策 / overrides TT−UTC; nil restores the built-in table and policy.
+func SetTTMinusUTC(ttMinusUTC func(float64) float64) {
+	basic.SetTTMinusUTCFn(ttMinusUTC)
+}
+
+// DefaultTTMinusUTC 返回内置闰秒表模型，忽略覆盖与未来政策 / built-in leap-table model, ignoring overrides and future policy.
+func DefaultTTMinusUTC() func(float64) float64 {
+	return basic.TTMinusUTCSecondsDefault
+}
+
+// TimeScaleFuturePolicy 民用时标换算政策，与输出用的 TimeScale 无关 / civil-time conversion policy, separate from output TimeScale.
+type TimeScaleFuturePolicy = basic.TimeScaleFuturePolicy
+
+const (
+	// TimeScaleLeapSecond 默认按 ΔT 越限施加整数秒校正，不代表闰秒公告 / default integer-second corrections driven by extrapolated ΔT, not announcements.
+	TimeScaleLeapSecond = basic.TimeScaleLeapSecond
+	// TimeScaleAssumeUT1Tracking 窗口外固定末端 DUT1，平滑跟随 UT1 / holds the last observed DUT1 beyond the window.
+	TimeScaleAssumeUT1Tracking = basic.TimeScaleAssumeUT1Tracking
+	// TimeScaleFreezeUTCOffset 假设 UTC 偏移冻结在精确窗口末端 / freezes the UTC offset at the window end.
+	TimeScaleFreezeUTCOffset = basic.TimeScaleFreezeUTCOffset
+	// TimeScaleLeapHour 按 ΔT 越限施加整小时校正，仅作情景演算 / applies hour-sized corrections as a scenario assumption.
+	TimeScaleLeapHour = basic.TimeScaleLeapHour
+	// TimeScaleUT1Civil 全时轴民用时标等同 UT1，TT−UTC 覆盖仍优先 / uses UT1 as civil time everywhere unless TT−UTC is overridden.
+	TimeScaleUT1Civil = basic.TimeScaleUT1Civil
+)
+
+// SetTimeScaleFuturePolicy 设置与 basic 共享的民用时标换算政策 / sets the civil-time conversion policy shared with basic.
+func SetTimeScaleFuturePolicy(policy TimeScaleFuturePolicy) {
+	basic.SetTimeScaleFuturePolicy(policy)
+}
+
+// GetTimeScaleFuturePolicy 返回当前民用时标换算政策 / current civil-time conversion policy.
+func GetTimeScaleFuturePolicy() TimeScaleFuturePolicy {
+	return basic.GetTimeScaleFuturePolicy()
+}
+
+// DeltaTModel 标识可选的已发布 ΔT 模型 / a selectable published ΔT model.
+type DeltaTModel = basic.DeltaTModel
+
+const (
+	// DeltaTModelDefault 内置默认：SMH2016 + Morrison 2021 / the built-in SMH2016 + Morrison 2021 model.
+	DeltaTModelDefault = basic.DeltaTModelDefault
+	// DeltaTModelSMH2016 显式选择内置模型 / selects the built-in model explicitly.
+	DeltaTModelSMH2016 = basic.DeltaTModelSMH2016
+	// DeltaTModelMS2004 Morrison & Stephenson 2004 长期抛物线 / the M&S2004 long-term parabola.
+	DeltaTModelMS2004 = basic.DeltaTModelMS2004
+	// DeltaTModelEspenakMeeus2006 Espenak & Meeus 2006 分段多项式 / the Espenak & Meeus 2006 piecewise polynomial.
+	DeltaTModelEspenakMeeus2006 = basic.DeltaTModelEspenakMeeus2006
+	// DeltaTModelNASACanon2006 上式再加配对修正 c，即 NASA 五千年目录的印刷口径 / plus the pairing term c, the NASA canon convention.
+	DeltaTModelNASACanon2006 = basic.DeltaTModelNASACanon2006
+	// DeltaTModelManual 表示当前生效的是 SetDeltaT 注入的任意函数 / an arbitrary function injected with SetDeltaT.
+	DeltaTModelManual = basic.DeltaTModelManual
+)
+
+// SetDeltaTModel 安装命名 ΔT 模型；keepObserved 为真时逐月实测段优先（推荐），未知模型返回 false 且不改动现状。
+// SetDeltaTModel installs a named ΔT model; with keepObserved the monthly observed span wins wherever it covers the instant.
+func SetDeltaTModel(model DeltaTModel, keepObserved bool) bool {
+	return basic.SetDeltaTModel(model, keepObserved)
+}
+
+// GetDeltaTModel 返回当前生效的模型与是否保留实测段 / the active model and whether the observed span is kept.
+func GetDeltaTModel() (DeltaTModel, bool) {
+	return basic.GetDeltaTModel()
+}
+
+// DeltaTModelSeconds 按命名模型求 ΔT（秒，入参为 UT 儒略日），不改变进程状态，便于对照 / evaluates a named model without touching process state.
+func DeltaTModelSeconds(model DeltaTModel, jd float64, keepObserved bool) float64 {
+	return basic.DeltaTModelSeconds(model, jd, keepObserved)
+}