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

geojson/solar_shadow_instant.go

@@ -52,7 +52,7 @@ func MarshalSolarEclipseShadowInstant(
 	regionProperties["source_boundary_closed"] = false
 	regionProperties["geometry_role"] = "horizon-closed-region"
 	regionProperties["closure"] = solarHorizonClosureProperties(
-		instant.Time, solarHorizonClosureExact(instant.Boundaries, instant.HorizonEnds),
+		instant.Time, instant.Time, solarHorizonClosureExact(instant.Boundaries, instant.HorizonEnds),
 	)
 	ring, boundary := solarShadowFootprintHorizonRing(
 		instant.Time, instant.Boundaries, instant.HorizonEnds, curve,