feat(excel-converters): 增强内置转换器功能，添加 StringArrayConverter.WRITE_INSTANCE

- 注册 StringArrayConverter.WRITE_INSTANCE 到 Excel 写构造器
- 优化代码格式，保持一致性

(cherry picked from commit 3800300f7f101560674dacc6a0840e279b753a2e)

pigx-common/pigx-common-excel/src/main/java/com/pig4cloud/pigx/common/excel/converters/BuiltinConverters.java

@@ -13,32 +13,31 @@ import java.util.List;
  */
 public final class BuiltinConverters {
 
-    private BuiltinConverters() {
-    }
+	private BuiltinConverters() {
+	}
 
-    /**
-     * 读写 Excel 时默认启用的转换器列表。
-     */
-    private static final List<Converter<?>> INSTANCES = List.of(LocalDateStringConverter.INSTANCE,
-            LocalTimeStringConverter.INSTANCE, LocalDateTimeStringConverter.INSTANCE, LongStringConverter.INSTANCE,
-            StringArrayConverter.INSTANCE);
+	/**
+	 * 读写 Excel 时默认启用的转换器列表。
+	 */
+	private static final List<Converter<?>> INSTANCES = List.of(LocalDateStringConverter.INSTANCE,
+			LocalTimeStringConverter.INSTANCE, LocalDateTimeStringConverter.INSTANCE, LongStringConverter.INSTANCE,
+			StringArrayConverter.INSTANCE);
 
-    /**
-     * 注册内置转换器到 Excel 写构造器。
-     *
-     * @param builder Excel 写构造器
-     */
-    public static void registerTo(ExcelWriterBuilder builder) {
-        INSTANCES.forEach(builder::registerConverter);
-    }
+	/**
+	 * 注册内置转换器到 Excel 写构造器。
+	 * @param builder Excel 写构造器
+	 */
+	public static void registerTo(ExcelWriterBuilder builder) {
+		INSTANCES.forEach(builder::registerConverter);
+		builder.registerConverter(StringArrayConverter.WRITE_INSTANCE);
+	}
 
-    /**
-     * 注册内置转换器到 Excel 读构造器。
-     *
-     * @param builder Excel 读构造器
-     */
-    public static void registerTo(ExcelReaderBuilder builder) {
-        INSTANCES.forEach(builder::registerConverter);
-    }
+	/**
+	 * 注册内置转换器到 Excel 读构造器。
+	 * @param builder Excel 读构造器
+	 */
+	public static void registerTo(ExcelReaderBuilder builder) {
+		INSTANCES.forEach(builder::registerConverter);
+	}
 
 }

pigx-common/pigx-common-excel/src/main/java/com/pig4cloud/pigx/common/excel/converters/StringArrayConverter.java

@@ -18,10 +18,20 @@ public enum StringArrayConverter implements Converter<String[]> {
 	/**
 	 * 实例
 	 */
-	INSTANCE;
+	INSTANCE,
+
+	/**
+	 * 未指定目标单元格类型时，FESOD 使用 null 作为导出转换器的类型键。
+	 */
+	WRITE_INSTANCE {
+		@Override
+		public CellDataTypeEnum supportExcelTypeKey() {
+			return null;
+		}
+	};
 
 	@Override
-    public Class<?> supportJavaTypeKey() {
+	public Class<?> supportJavaTypeKey() {
 		return String[].class;
 	}
 
@@ -31,15 +41,15 @@ public enum StringArrayConverter implements Converter<String[]> {
 	}
 
 	@Override
-    public String[] convertToJavaData(ReadCellData<?> cellData, ExcelContentProperty contentProperty,
-                                      GlobalConfiguration globalConfiguration) {
-        return StrUtil.splitToArray(cellData.getStringValue(), StrUtil.COMMA);
+	public String[] convertToJavaData(ReadCellData<?> cellData, ExcelContentProperty contentProperty,
+			GlobalConfiguration globalConfiguration) {
+		return StrUtil.splitToArray(cellData.getStringValue(), StrUtil.COMMA);
 	}
 
 	@Override
 	public WriteCellData<String> convertToExcelData(String[] value, ExcelContentProperty contentProperty,
 			GlobalConfiguration globalConfiguration) {
-        return new WriteCellData<>(String.join(StrUtil.COMMA, value));
+		return new WriteCellData<>(String.join(StrUtil.COMMA, value));
 	}
 
 }