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

moon/svg/occultation_panel_fit_test.go

@@ -0,0 +1,47 @@
+package svg
+
+import (
+	"errors"
+	"testing"
+)
+
+// 数据块行距不足时详细版必须拒绝画布，而不是画出压叠的面板文字。
+func TestOccultationDetailedSVGRejectsCanvasesThatCrowdPanels(t *testing.T) {
+	for _, testCase := range []struct {
+		name          string
+		width, height int
+		rejected      bool
+	}{
+		{name: "landscape too short", width: 900, height: 400, rejected: true},
+		{name: "landscape borderline", width: 900, height: 560, rejected: true},
+		{name: "portrait too narrow", width: 600, height: 800, rejected: true},
+		{name: "smallest landscape", width: 800, height: 600},
+		{name: "default page", width: 1000, height: 1414},
+		{name: "landscape page", width: 1414, height: 1000},
+	} {
+		for name, render := range map[string]func() (string, error){
+			"star": func() (string, error) {
+				return StarOccultationDetailedSVG(occultationTestStarPath(t), hr4799StarCoordinate(),
+					OccultationDetailedSVGOptions{Width: testCase.width, Height: testCase.height})
+			},
+			"planet": func() (string, error) {
+				return PlanetOccultationDetailedSVG(occultationTestSaturnPath(t),
+					OccultationDetailedSVGOptions{Width: testCase.width, Height: testCase.height})
+			},
+		} {
+			document, err := render()
+			if testCase.rejected {
+				if !errors.Is(err, ErrInvalidOccultationDetailedSVGOptions) {
+					t.Fatalf("%s %s: err = %v, want ErrInvalidOccultationDetailedSVGOptions", name, testCase.name, err)
+				}
+				continue
+			}
+			if err != nil {
+				t.Fatalf("%s %s: %v", name, testCase.name, err)
+			}
+			if len(document) == 0 {
+				t.Fatalf("%s %s: empty document", name, testCase.name)
+			}
+		}
+	}
+}