feat: 完善时标与天象几何计算并扩展输出接口

- 新增时标、ΔT 模型、质心时间与 UT1 支持
- 改进日月食、月掩、行星事件及路径边界计算
- 完善恒星三维自行与动态距离传播
- 扩展 SVG、GeoJSON、KML 输出与底层距离换算工具
- 整理中英文手册、示例资源及回归测试

eclipse/svg/solar_map_timescale_test.go

@@ -0,0 +1,55 @@
+package svg
+
+import (
+	"regexp"
+	"strings"
+	"testing"
+	"time"
+
+	"b612.me/astro"
+)
+
+// 太阳能图的 UT1 输出只改时刻文字：直射点、闭合弧与等时线几何必须逐字节相同。
+// 时刻标记按输出时标的整点取点（UT1 整点是另一个物理时刻），与文字一起从比较里剔除。
+func TestSolarEclipseMapUT1KeepsGeometry(t *testing.T) {
+	for _, date := range []time.Time{
+		time.Date(2021, time.June, 10, 12, 0, 0, 0, time.UTC),    // DUT1 较大，直射点位移可测
+		time.Date(1995, time.October, 24, 12, 0, 0, 0, time.UTC), // 双向极限事件
+		time.Date(2024, time.April, 8, 12, 0, 0, 0, time.UTC),
+	} {
+		options := SolarEclipseMapSVGOptions{
+			Width: 1200, Height: 800, Location: time.UTC, TimeLabelStep: 30 * time.Minute,
+		}
+		utc, ok := SolarEclipseMapSVG(date, options)
+		if !ok {
+			t.Fatalf("%s: UTC render failed", date.Format("2006-01-02"))
+		}
+		ut1Options := options
+		ut1Options.TimeScale = astro.TimeScaleUT1
+		ut1, ok := SolarEclipseMapSVG(date, ut1Options)
+		if !ok {
+			t.Fatalf("%s: UT1 render failed", date.Format("2006-01-02"))
+		}
+		if !strings.Contains(ut1, "DUT1 = UT1−UTC") {
+			t.Errorf("%s: UT1 chart does not declare the DUT1 offset", date.Format("2006-01-02"))
+		}
+		cst := time.FixedZone("CST", 8*3600)
+		badOptions := ut1Options
+		badOptions.Location = cst
+		if _, ok := SolarEclipseMapSVG(date, badOptions); ok {
+			t.Errorf("%s: UT1 with a non-UTC location must fail", date.Format("2006-01-02"))
+		}
+		if stripSolarTimescaleText(utc) != stripSolarTimescaleText(ut1) {
+			t.Errorf("%s: switching to UT1 changed chart geometry", date.Format("2006-01-02"))
+		}
+	}
+}
+
+var (
+	solarTimescaleText    = regexp.MustCompile(`(?s)<text[^>]*>.*?</text>`)
+	solarTimescaleMarkers = regexp.MustCompile(`(?s)<g class="solar-time-marker">.*?</g>`)
+)
+
+func stripSolarTimescaleText(doc string) string {
+	return solarTimescaleText.ReplaceAllString(solarTimescaleMarkers.ReplaceAllString(doc, ""), "")
+}