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

geojson/mars20250729_fixture_test.go

@@ -0,0 +1,76 @@
+package geojson_test
+
+import (
+	"sync"
+	"testing"
+	"time"
+
+	"b612.me/astro/geojson"
+	"b612.me/astro/moon"
+)
+
+type mars20250729FixtureKey struct {
+	riseSetStep     time.Duration
+	includeTimeline bool
+}
+
+type mars20250729Fixture struct {
+	path       moon.PlanetOccultationPath
+	collection decodedCollection
+}
+
+var mars20250729Fixtures = struct {
+	sync.Mutex
+	values map[mars20250729FixtureKey]*mars20250729Fixture
+}{values: make(map[mars20250729FixtureKey]*mars20250729Fixture)}
+
+// mars20250729TestFixture computes each distinct Mars regression scenario once.
+// The returned path and decoded collection are read-only test fixtures; caching
+// them avoids repeating the expensive ephemeris and GeoJSON setup in related
+// assertions without sharing mutable production state.
+func mars20250729TestFixture(
+	t *testing.T,
+	riseSetStep time.Duration,
+	includeTimeline bool,
+) *mars20250729Fixture {
+	t.Helper()
+	key := mars20250729FixtureKey{
+		riseSetStep:     riseSetStep,
+		includeTimeline: includeTimeline,
+	}
+
+	mars20250729Fixtures.Lock()
+	defer mars20250729Fixtures.Unlock()
+	if fixture := mars20250729Fixtures.values[key]; fixture != nil {
+		return fixture
+	}
+
+	zone := time.FixedZone("UTC+8", 8*60*60)
+	start := time.Date(2025, time.July, 29, 0, 0, 0, 0, zone)
+	options := moon.OccultationPathOptions{
+		Step:              20 * time.Minute,
+		TargetSpacingKM:   900,
+		RiseSetStep:       riseSetStep,
+		DisableFootprints: true,
+	}
+	if includeTimeline {
+		options.IncludeFootprintTimeline = true
+		options.FootprintTimelineStep = 5 * time.Minute
+	}
+	paths, err := moon.FindPlanetOccultationPaths(
+		start, start.Add(24*time.Hour), moon.OccultationMars, options,
+	)
+	if err != nil || len(paths) != 1 {
+		t.Fatalf("FindPlanetOccultationPaths() paths=%d err=%v, want one", len(paths), err)
+	}
+	data, err := geojson.MarshalPlanetOccultation(paths[0])
+	if err != nil {
+		t.Fatalf("MarshalPlanetOccultation: %v", err)
+	}
+	fixture := &mars20250729Fixture{
+		path:       paths[0],
+		collection: decodeCollection(t, data),
+	}
+	mars20250729Fixtures.values[key] = fixture
+	return fixture
+}