- 新增 seam_fallback_label 纯函数:前缀匹配转换 seam* → seam_fallback*,保留后缀 - main() 调用改为函数式,避免等值判断失效 - 测试覆盖:plain seam、seam+uvpm、smart_fallback 透传 Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>