fix: WinForms导出Rime等格式时传递用户选择的编码类型到转换管道

修复 #398

问题原因：WinForms GUI 在用户选择导出格式（如Rime）时，虽然弹出了配置对话框
让用户选择编码类型（拼音/五笔等），但关闭对话框后从未读取用户的选择，导致
ConversionRequest 中 CodeGenerationOptions.TargetCodeType 始终为 NoCode。

转换管道跳过编码生成 → 所有词条 Code 为 null → Rime 导出器对无编码词条输出
空行 → 最终文件内容为空，但界面仍提示成功。

修复方式：
- 新增 _selectedCodeType 字段保存用户选择
- ShowDialog 返回后从各配置表单读取 SelectedCodeType
- 将 _selectedCodeType 传入 ConversionRequest.Options.CodeGeneration

Author: studyzy

src/IME WL Converter Win/Forms/MainForm.cs

@@ -45,6 +45,7 @@ public partial class MainForm : Form
     private IFormatExporter? _selectedExporter;
 
     private ChineseConversionMode _chineseConversionMode = ChineseConversionMode.None;
+    private CodeType _selectedCodeType = CodeType.NoCode;
 
     private FilterConfig filterConfig = new();
     private IWordRankGenerator _wordRankGenerator;
@@ -159,9 +160,26 @@ private void cbxTo_SelectedIndexChanged(object sender, EventArgs e)
             if (form != null)
             {
                 if (form is SelfDefiningConfigForm selfDefForm)
+                {
                     selfDefForm.ShowDialog();
+                }
                 else
+                {
                     form.ShowDialog();
+                }
+
+                if (form.DialogResult == DialogResult.OK)
+                {
+                    _selectedCodeType = form switch
+                    {
+                        RimeConfigForm f => f.SelectedCodeType,
+                        XiaoxiaoConfigForm f => f.SelectedCodeType,
+                        ErbiTypeForm f => f.SelectedCodeType,
+                        PinyinConfigForm f => f.SelectedCodeType,
+                        PhraseFormatConfigForm f => f.SelectedCodeType,
+                        _ => CodeType.NoCode
+                    };
+                }
             }
         }
     }
@@ -380,7 +398,11 @@ private async void btnConvert_Click(object? sender, EventArgs e)
             FilterConfig = filterConfig,
             Options = new ConversionOptions
             {
-                ChineseConversion = _chineseConversionMode
+                ChineseConversion = _chineseConversionMode,
+                CodeGeneration = new CodeGenerationOptions
+                {
+                    TargetCodeType = _selectedCodeType
+                }
             }
         };