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

basic/occultation_planet_path.go

@@ -548,7 +548,7 @@ func occultationPathBoundarySamplesAtTimesForFrame(
 	first := make([]OccultationPathPoint, len(samples))
 	second := make([]OccultationPathPoint, len(samples))
 	for index, sample := range samples {
-		siderealDegrees := ApparentSiderealTime(TD2UT(sample.tt, false)) * 15
+		siderealDegrees := ApparentSiderealTime(TT2UT1(sample.tt)) * 15
 		first[index] = occultationPathPointFromVectorWithMoonSidereal(
 			sample.tt, sample.first, 0, sample.moon, siderealDegrees, location,
 		)
@@ -1532,6 +1532,11 @@ func occultationPathLimitsAndWidthForFrame(
 					consider(point)
 				}
 			}
+			// 末样本的等差写法与 rightTheta 相差 1 ULP：掠射时该 ULP 会把端点的判别式推成负值，
+			// 端点处的横向极值就被当成"无地面交点"丢掉，故端点原值必须补采一次。
+			if point, _, pointOK := occultationPathBoundaryVector(frame, rightTheta); pointOK {
+				consider(point)
+			}
 		}
 	}
 	for i := 0; i < occultationPathBoundaryScanPoints; i++ {
@@ -1641,6 +1646,11 @@ func occultationPathFiniteCrossTrackExtrema(
 					consider(point)
 				}
 			}
+			// 末样本的等差写法与 rightTheta 相差 1 ULP：掠射时该 ULP 会把端点的判别式推成负值，
+			// 端点处的极值就被当成"无地面交点"丢掉，故端点原值必须补采一次。
+			if point, _, pointOK := occultationPathBoundaryVector(frame, rightTheta); pointOK {
+				consider(point)
+			}
 		}
 	}
 	for _, interval := range occultationPathBoundaryThetaIntervals(frame) {
@@ -1650,6 +1660,11 @@ func occultationPathFiniteCrossTrackExtrema(
 				consider(point)
 			}
 		}
+		// 与 occultationPathLimitsAndWidthForFrame 同因：等差末样本与 interval.right 差 1 ULP，
+		// 掠射时会把端点判别式推成负值而丢掉该处极值，端点原值必须补采一次。
+		if point, _, pointOK := occultationPathBoundaryVector(frame, interval.right); pointOK {
+			consider(point)
+		}
 	}
 	if !finite(minimumOffset) || !finite(maximumOffset) {
 		return occultationPathVector{}, occultationPathVector{}, 0, false