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

basic/solar_eclipse_shadow_batch_test.go

@@ -0,0 +1,61 @@
+package basic
+
+import "testing"
+
+// 批量入口是导出契约的一部分，必须与逐时刻入口给出同一条数值链。
+func TestSolarEclipseShadowBatchEntriesMatchPerInstantCalls(t *testing.T) {
+	footprints := SolarEclipsePartialFootprints(JDECalc(2009, 7, 22), SolarEclipsePartialFootprintOptions{
+		StepDays: 6.0 / 1440.0, BoundaryPoints: 48, DisableRiseSetCurves: true,
+		CentralShadowStepDays: 6.0 / 1440.0,
+	})
+	if len(footprints.CentralShadowFootprints) < 3 {
+		t.Fatalf("central shadow samples=%d, want a full series", len(footprints.CentralShadowFootprints))
+	}
+	options := SolarEclipseShadowSolverOptions{}
+	step := 6.0 / 1440.0
+	start := footprints.CentralShadowFootprints[0].JDE
+	end := start + 4*step
+	batch := SolarEclipseShadowBetweenJDE(start, end, step, options)
+	if len(batch) != 5 {
+		t.Fatalf("batch length=%d, want 5", len(batch))
+	}
+	nonEmpty := 0
+	for index, instant := range batch {
+		direct, ok := SolarEclipseShadowAtJDE(start+float64(index)*step, options)
+		if ok != !direct.Empty() {
+			t.Fatalf("instant %d ok=%v, Empty=%v", index, ok, direct.Empty())
+		}
+		if instant.Empty() != direct.Empty() || len(instant.Boundaries) != len(direct.Boundaries) {
+			t.Fatalf("instant %d batch=%d segments, direct=%d", index, len(instant.Boundaries), len(direct.Boundaries))
+		}
+		if !instant.Empty() {
+			nonEmpty++
+		}
+	}
+	if nonEmpty == 0 {
+		t.Fatal("batch reported no shadow anywhere along the central path")
+	}
+	longitude, latitude := footprints.Eclipse.GreatestLongitude, footprints.Eclipse.GreatestLatitude
+	solver := NewSolarEclipseShadowSolver(options)
+	states := solver.StationStatesBetweenJDE(start, end, step, longitude, latitude, 0)
+	if len(states) != len(batch) {
+		t.Fatalf("station state batch length=%d, want %d", len(states), len(batch))
+	}
+	for index, state := range states {
+		direct := SolarEclipseStationStateAtJDE(start+float64(index)*step, longitude, latitude, 0, options)
+		if state != direct {
+			t.Fatalf("station state %d = %+v, want %+v", index, state, direct)
+		}
+	}
+	for _, badStep := range []float64{0, -step} {
+		if got := SolarEclipseShadowBetweenJDE(start, end, badStep, options); got != nil {
+			t.Fatalf("step %v produced %d instants, want nil", badStep, len(got))
+		}
+	}
+	if got := solver.ShadowBetweenJDE(end, start, step); got != nil {
+		t.Fatalf("reversed window produced %d instants, want nil", len(got))
+	}
+	if got := SolarEclipseShadowBetweenJDE(start, start+10, 1e-9, options); got != nil {
+		t.Fatalf("oversized batch produced %d instants, want nil", len(got))
+	}
+}