fix: 兼容 TinyGo wasm 编译行星星历初始化

- 将 planetViews 从包级初始化改为 sync.Once 懒加载，避免 TinyGo interp 在编译期处理大型 float64 表切片索引时触发 unsupported fcmp
- 将行星视图构建失败改为内部返回 error，并由兼容层统一 panic
- 补充无效行星数据切片边界测试

planet/planet_test.go

@@ -25,8 +25,9 @@ func TestWherePlanetNFullMatchesDefault(t *testing.T) {
 }
 
 func TestPlanetViewsMatchRawCuts(t *testing.T) {
+	views := planetViews()
 	for bodyIndex, raw := range planetRawData {
-		view := planetViews[bodyIndex]
+		view := views[bodyIndex]
 		if math.Float64bits(view.scale) != math.Float64bits(raw[0]) {
 			t.Fatalf("body=%d scale mismatch", bodyIndex)
 		}
@@ -42,3 +43,15 @@ func TestPlanetViewsMatchRawCuts(t *testing.T) {
 		}
 	}
 }
+
+func TestBuildPlanetViewsRejectsInvalidCuts(t *testing.T) {
+	_, err := buildPlanetViews([][]float64{{
+		10000000000,
+		20, 21, 20, 20, 20, 20, 20,
+		20, 20, 20, 20, 20, 20,
+		20, 20, 20, 20, 20, 20,
+	}})
+	if err == nil {
+		t.Fatal("expected invalid cut error")
+	}
+}