feat: 新增月掩与日月食地理绘图并提升观测计算精度

- 新增月掩恒星和行星：支持搜索、掩甚点、全球掩带及固定地点轨迹计算
- 支持恒星星表坐标转换、有限盘面行星接触事件和月掩 SVG 输出
- 新增日月食及月掩全球投影图、时间标记和 GeoJSON 地理数据接口
- 扩展日食中心线、南北界及偏食足迹采样，支持极区投影
- 修正站心时角、月出月落、月球视半径、折射和恒星自行计算
- 优化内外行星事件搜索、边界选择、极端输入处理和计算稳定性

basic/occultation_planet_footprint_test.go

@@ -0,0 +1,116 @@
+package basic
+
+import (
+	"errors"
+	"math"
+	"testing"
+	"time"
+)
+
+func TestPlanetOccultationSaturnFootprintsContainCenterLine(t *testing.T) {
+	config, ok := planetOccultationConfigFor(OccultationSaturn)
+	if !ok {
+		t.Fatal("Saturn occultation config is unavailable")
+	}
+	seedTT := occultationTimeToTT(time.Date(2025, time.February, 1, 4, 0, 48, 0, time.UTC))
+	for _, contact := range []struct {
+		name    string
+		frameAt occultationPathFrameFunc
+	}{
+		{name: "partial", frameAt: func(tt float64) (occultationPathFrame, bool) {
+			return planetOccultationPathFrameAt(tt, config)
+		}},
+		{name: "total", frameAt: func(tt float64) (occultationPathFrame, bool) {
+			return planetOccultationTotalPathFrameAt(tt, config)
+		}},
+	} {
+		startTT, endTT, found := occultationPathWindowForFrame(
+			seedTT, seedTT-occultationPathSearchSpanDays, seedTT+occultationPathSearchSpanDays,
+			contact.frameAt, true,
+		)
+		if !found {
+			t.Fatalf("%s center interval is unavailable", contact.name)
+		}
+		checked := 0
+		for tt := startTT + 2.0/1440.0; tt < endTT-2.0/1440.0; tt += 5.0 / 1440.0 {
+			frame, frameOK := contact.frameAt(tt)
+			center, _, centerOK := occultationEarthLineIntersection(frame.moon, frame.axis)
+			footprint, footprintOK := planetOccultationFootprintAt(tt, contact.frameAt, time.UTC)
+			if !frameOK || !centerOK || !footprintOK {
+				t.Fatalf("%s center or footprint is unavailable at TT %.9f", contact.name, tt)
+			}
+			longitude, latitude := occultationPathGeodetic(tt, center)
+			if !planetOccultationFootprintContains(footprint, longitude, latitude) {
+				t.Fatalf("%s footprint does not contain center %.6f, %.6f at TT %.9f",
+					contact.name, longitude, latitude, tt)
+			}
+			checked++
+		}
+		if checked < 10 {
+			t.Fatalf("%s checked only %d center samples", contact.name, checked)
+		}
+	}
+}
+
+func TestPlanetOccultationPathRejectsExcessiveAggregateSampling(t *testing.T) {
+	start := time.Date(2025, time.February, 1, 0, 0, 0, 0, time.UTC)
+	_, err := FindPlanetOccultationPaths(
+		start, start.Add(24*time.Hour), OccultationSaturn,
+		OccultationPathOptions{Step: time.Second},
+	)
+	if !errors.Is(err, ErrOccultationPathSamplingLimit) {
+		t.Fatalf("FindPlanetOccultationPaths() error = %v, want ErrOccultationPathSamplingLimit", err)
+	}
+}
+
+func TestPlanetOccultationFootprintsHaveIndependentSampleBudget(t *testing.T) {
+	times := occultationPathSampleTimesWithLimit(
+		0, 1, 0.500001, 1.0/86400.0, planetOccultationFootprintMaxSamples,
+	)
+	if len(times) > planetOccultationFootprintMaxSamples {
+		t.Fatalf("footprint sample count = %d, maximum %d", len(times), planetOccultationFootprintMaxSamples)
+	}
+	foundGreatest := false
+	for _, sample := range times {
+		if sample == 0.500001 {
+			foundGreatest = true
+			break
+		}
+	}
+	if !foundGreatest {
+		t.Fatal("bounded footprint samples omitted greatest")
+	}
+}
+
+func planetOccultationFootprintContains(
+	footprint PlanetOccultationFootprint,
+	longitude, latitude float64,
+) bool {
+	for _, polygon := range footprint.Polygons {
+		inside := false
+		for current, previous := 0, len(polygon)-1; current < len(polygon); previous, current = current, current+1 {
+			currentX := math.Remainder(polygon[current].Longitude-longitude, 360)
+			previousX := math.Remainder(polygon[previous].Longitude-longitude, 360)
+			currentY := polygon[current].Latitude
+			previousY := polygon[previous].Latitude
+			if math.Abs(currentX-previousX) > 180 {
+				if currentX < previousX {
+					currentX += 360
+				} else {
+					previousX += 360
+				}
+			}
+			if (currentY > latitude) == (previousY > latitude) {
+				continue
+			}
+			intersectionX := previousX + (latitude-previousY)*(currentX-previousX)/(currentY-previousY)
+			if intersectionX > 0 {
+				inside = !inside
+			}
+		}
+		if inside {
+			return true
+		}
+	}
+	return false
+}