feat: 完善水星与金星全球凌日搜索及制图导出

- 基于平均下合周期与节点相位预筛候选，减少无效星历计算；跳过无法求解的单个会合周期，避免有限覆盖星历导致搜索提前终止
- 引入影轴 γ、半影半径及地球尺度几何判定，结合站心可见性识别地心无接触、仅部分地区可见的掠凌
- 添加金星 243 年、水星 46 年周期族编号，并明确编号适用范围及未分配时的零值语义
- 为 SVG、GeoJSON 和 KML 增加站心部分凌日可见区，适配接触等时线、几何元数据、图层样式及取景；为地心无接触凌日事件增加正射图，按可见区球面面积加权居中

eclipse/svg/transit_partial_test.go

@@ -0,0 +1,106 @@
+package svg
+
+import (
+	"regexp"
+	"strconv"
+	"strings"
+	"testing"
+	"time"
+)
+
+func TestTransitSVGGlobalPartial(tester *testing.T) {
+	date := time.Date(2854, 12, 14, 0, 0, 0, 0, time.UTC)
+	chart, ok := TransitMapSVG(TransitVenus, date, TransitMapSVGOptions{Isochrones: TransitIsochroneAll, IsochroneStep: 30 * time.Second})
+	if !ok {
+		tester.Fatal("global partial transit render failed")
+	}
+	for _, expected := range []string{"2854-12-14", "transit-partial-region", "地心无接触", "周期族 4", "γ ", "c1-isochrone", "c4-isochrone"} {
+		if !strings.Contains(chart, expected) {
+			tester.Fatalf("missing %s", expected)
+		}
+	}
+	for _, absent := range []string{"NaN", "Inf", "transit-sun-c1-shape", "c2-isochrone", "c3-isochrone"} {
+		if strings.Contains(chart, absent) {
+			tester.Fatalf("invalid SVG contains %s", absent)
+		}
+	}
+	local, ok := TransitLocalSVG(TransitVenus, date, -135, -60, 0, TransitLocalSVGOptions{})
+	if !ok || !strings.Contains(local, "transit-planet-c1") || !strings.Contains(local, "transit-planet-c4") || strings.Contains(local, "transit-planet-c2") {
+		tester.Fatal("local partial-transit diagram has invalid contacts")
+	}
+	labels := regexp.MustCompile(`class="transit-event-label" x="[0-9.-]+" y="([0-9.-]+)"`).FindAllStringSubmatch(local, -1)
+	if len(labels) != 3 {
+		tester.Fatalf("grazing contact labels=%d, want 3", len(labels))
+	}
+	footer := regexp.MustCompile(`<text x="40" y="([0-9.-]+)" fill="#555"`).FindAllStringSubmatch(local, -1)
+	if len(footer) == 0 {
+		tester.Fatal("local partial-transit diagram has no footer")
+	}
+	firstFooterBaseline, _ := strconv.ParseFloat(footer[0][1], 64)
+	for _, label := range labels {
+		baseline, _ := strconv.ParseFloat(label[1], 64)
+		if baseline > firstFooterBaseline-8 {
+			tester.Fatal("contact label overlaps the footer")
+		}
+	}
+	if _, ok := TransitLocalSVG(TransitVenus, date, 0, 45, 0, TransitLocalSVGOptions{}); ok {
+		tester.Fatal("a northern site must miss the transit")
+	}
+}
+
+func TestTransitMapLegendListsDrawnIsochrones(tester *testing.T) {
+	for _, test := range []struct {
+		planet TransitPlanet
+		date   time.Time
+		inner  bool
+	}{
+		{TransitVenus, time.Date(554, 5, 22, 0, 0, 0, 0, time.UTC), true},
+		{TransitMercury, time.Date(-513, 10, 22, 0, 0, 0, 0, time.UTC), false},
+	} {
+		chart, ok := TransitMapSVG(test.planet, test.date, TransitMapSVGOptions{Isochrones: TransitIsochroneAll, Language: "en"})
+		if !ok {
+			tester.Fatalf("%v: render failed", test.date)
+		}
+		for _, marker := range []string{"c2-isochrone", "C2 isochrones", "C3 isochrones"} {
+			if strings.Contains(chart, marker) != test.inner {
+				tester.Fatalf("%v: %s present=%v, want %v", test.date, marker, !test.inner, test.inner)
+			}
+		}
+	}
+}
+
+// 地心无接触的部分凌日也要在图例里列出实际画出的一触、四触等时线；二触、三触不存在。
+func TestTransitPartialLegendListsDrawnIsochrones(tester *testing.T) {
+	for _, language := range []string{"zh", "en"} {
+		chart, ok := TransitMapSVG(TransitVenus, time.Date(2854, 12, 14, 0, 0, 0, 0, time.UTC), TransitMapSVGOptions{
+			Isochrones: TransitIsochroneAll, Language: language,
+		})
+		if !ok {
+			tester.Fatalf("%s: render failed", language)
+		}
+		partial, c1, c4 := "部分凌日可见区", "一触等时线", "四触等时线"
+		if language == "en" {
+			partial, c1, c4 = "Partial transit visible", "C1 isochrones", "C4 isochrones"
+		}
+		for _, expected := range []string{"c1-isochrone", "c4-isochrone", partial, c1, c4} {
+			if !strings.Contains(chart, expected) {
+				tester.Fatalf("%s: partial chart is missing %q", language, expected)
+			}
+		}
+		for _, absent := range []string{"c2-isochrone", "c3-isochrone", "二触等时线", "三触等时线", "C2 isochrones", "C3 isochrones"} {
+			if strings.Contains(chart, absent) {
+				tester.Fatalf("%s: partial chart must not contain %q", language, absent)
+			}
+		}
+	}
+	// 默认不画等时线时图例只留可见区色块，不凭空加等时线条目。
+	chart, ok := TransitMapSVG(TransitVenus, time.Date(2854, 12, 14, 0, 0, 0, 0, time.UTC), TransitMapSVGOptions{Language: "en"})
+	if !ok {
+		tester.Fatal("default render failed")
+	}
+	for _, absent := range []string{"c1-isochrone", "C1 isochrones", "C4 isochrones"} {
+		if strings.Contains(chart, absent) {
+			tester.Fatalf("default chart must not contain %q", absent)
+		}
+	}
+}