feat(web): 项目级配置 + 会话命名/历史 + 设计文档纳入影响调查

- 会话支持 name/project 字段，上传要件定义后自动命名；前端侧边栏会话历史 + localStorage 恢复，顶部只显示会话名
- 新增 ProjectsStore（SQLite）与 /api/projects CRUD；绑定项目后 _rebuild_source 合并模板/规则/代码库/设计文档，上传区仅要件定义
- StructuredSource.design_docs 与 ImpactReport.design_references；影响调查新增既有设计文档确定性交叉引用（无 LLM）
- 同步更新 docs/design.md §12.7、README、_AI_USAGE_LOG.md；全量测试 558 通过，覆盖率 99.10%

src/genesis/impact/impact_agent.py

@@ -7,11 +7,13 @@ from __future__ import annotations
 
 import logging
 from datetime import date
+from pathlib import Path
 
 from genesis.data_models import (
     ChangeAnalysis,
     ChangeElement,
     ChangeType,
+    DesignReference,
     ExcelTable,
     ImpactReport,
     ImpactWarning,
@@ -66,6 +68,10 @@ def impact_report_to_dict(report: ImpactReport) -> dict:
             "warnings": [{"element_id": w.element_id, "issue": w.issue} for w in ca.warnings],
         },
         "summary": dict(report.summary),
+        "design_references": [
+            {"doc_name": r.doc_name, "identifier": r.identifier, "snippet": r.snippet}
+            for r in report.design_references
+        ],
     }
 
 
@@ -124,6 +130,7 @@ class ImpactAgent:
             "unchanged": unchanged,
             "warnings": len(warnings),
         }
+        design_references = self._cross_ref_design_docs(structured_source, lookup)
         return ImpactReport(
             metadata={
                 "version": "v1",
@@ -134,8 +141,40 @@ class ImpactAgent:
             },
             change_analysis=change_analysis,
             summary=summary,
+            design_references=design_references,
         )
 
+    def _cross_ref_design_docs(
+        self, structured_source: StructuredSource, lookup: dict[str, list[dict]]
+    ) -> list[DesignReference]:
+        """既有设计文档确定性交叉引用（Type A 辅助证据）。
+
+        以既有系统（existing_system）解析出的标识符（类/方法/模块名）为锚，
+        在 design_docs 的 markdown 文本中检索命中，输出 DesignReference 列表。
+        无 LLM 参与，纯字符串匹配。
+        """
+        design_docs = getattr(structured_source, "design_docs", []) or []
+        if not design_docs:
+            return []
+        identifiers = [k for k in lookup.keys() if len(k) >= 3]
+        refs: list[DesignReference] = []
+        for doc in design_docs:
+            text = getattr(doc, "markdown_content", "") or ""
+            if not text:
+                continue
+            doc_name = Path(getattr(doc, "source_path", "design.docx")).name
+            text_lower = text.lower()
+            for ident in identifiers:
+                il = ident.lower()
+                idx = text_lower.find(il)
+                if idx >= 0:
+                    token = text[idx:idx + len(il)]  # 设计文档中的原始大小写
+                    start = max(0, idx - 30)
+                    end = min(len(text), idx + len(il) + 30)
+                    snippet = text[start:end].replace("\n", " ").strip()
+                    refs.append(DesignReference(doc_name=doc_name, identifier=token, snippet=snippet))
+        return refs
+
     # ---------- 内部 ----------
 
     def _classify_table(