Software maintainability critically depends on high-quality requirements descriptions and explicit traceability between requirements and code. Although automated code summarization (ACS) and requirements traceability (RT) techniques have been widely studied, existing ACS methods mainly generate implementation-level (i.e., developer-oriented) requirements (IRs) for fine-grained units (e.g., methods), while RT techniques often overlook the impact of project evolution. As a result, user-level (i.e., end user-oriented) requirements (URs) and live trace links remain underexplored, despite their importance for supporting user understanding and for validating whether AI-generated software aligns with user intent. To address this gap, we propose UserTrace, a multi-agent system that automatically generates URs and recovers live trace links (from URs to IRs to code) from software repositories. UserTrace coordinates four specialized agents (i.e., Code Reviewer, Searcher, Writer, and Verifier) through a three-phase process: structuring repository dependencies, deriving IRs for code units, and synthesizing URs with domain-specific context. Our comparative evaluation shows that UserTrace produces URs with higher completeness, correctness, and helpfulness than an established baseline, and achieves superior precision in trace link recovery compared to five state-of-the-art RT approaches. A user study further demonstrates that UserTrace helps end users validate whether the AI-generated repositories align with their intent.