SQLite 持久连接 — sandbox 不再每次查询开关连接，改为 __init__ 时建连、close() 时释放

Explorer 的 system prompt 明确告知 sandbox 规则 — "每条 SQL 必须包含聚合函数或 LIMIT"，减少 LLM 生成违规 SQL 浪费轮次
LLM 客户端单例 — 所有组件共享一个 openai.OpenAI 实例，不再各建各的
sanitize 顺序修复 — 小样本抑制放在 float round 之前，避免被 round 干扰
quick_detect 从 O(n²) 改为 O(n) — 按列聚合一次，加去重，不再对每行重复算整列统计
历史上下文实际生效 — get_context_for 的结果现在会注入到 Explorer 的初始 prompt 里，多轮分析时 LLM 能看到之前的发现

layers/context.py

@@ -0,0 +1,80 @@
+"""
+Layer 4: 上下文管理器
+"""
+import time
+from dataclasses import dataclass, field
+from typing import Optional
+
+from layers.explorer import ExplorationStep
+from layers.insights import Insight
+
+
+@dataclass
+class AnalysisSession:
+    """一次分析的完整记录"""
+    question: str
+    plan: dict
+    steps: list[ExplorationStep]
+    insights: list[Insight]
+    report: str
+    timestamp: float = field(default_factory=time.time)
+
+    def summary(self) -> str:
+        parts = [f"**问题**: {self.question}"]
+        if self.plan:
+            parts.append(f"**分析类型**: {self.plan.get('analysis_type', 'unknown')}")
+            parts.append(f"**维度**: {', '.join(self.plan.get('dimensions', []))}")
+        key_findings = []
+        for step in self.steps:
+            if step.success and step.rows:
+                top_row = step.rows[0] if step.rows else {}
+                finding = f"{step.purpose}: " + ", ".join(f"{k}={v}" for k, v in top_row.items() if k.lower() != "id")
+                key_findings.append(finding)
+        if key_findings:
+            parts.append("**核心发现**:")
+            for f in key_findings[:5]:
+                parts.append(f"  - {f}")
+        if self.insights:
+            parts.append("**洞察**:")
+            for i in self.insights[:3]:
+                parts.append(f"  - {i}")
+        return "\n".join(parts)
+
+    def to_reference_text(self) -> str:
+        return (
+            f"## 之前的分析\n### 问题\n{self.question}\n### 摘要\n{self.summary()}\n### 发现\n"
+            + "\n".join(f"- {s.purpose}: {s.row_count} 行" for s in self.steps if s.success)
+        )
+
+
+class ContextManager:
+    """上下文管理器"""
+
+    def __init__(self, max_history: int = 10):
+        self.sessions: list[AnalysisSession] = []
+        self.max_history = max_history
+
+    def add_session(self, question: str, plan: dict, steps: list[ExplorationStep],
+                    insights: list[Insight], report: str) -> AnalysisSession:
+        session = AnalysisSession(question=question, plan=plan, steps=steps, insights=insights, report=report)
+        self.sessions.append(session)
+        if len(self.sessions) > self.max_history:
+            self.sessions = self.sessions[-self.max_history:]
+        return session
+
+    def get_context_for(self, new_question: str) -> Optional[str]:
+        if not self.sessions:
+            return None
+        return "\n\n---\n\n".join(s.to_reference_text() for s in self.sessions[-2:])
+
+    def get_history_summary(self) -> str:
+        if not self.sessions:
+            return "（无历史分析）"
+        lines = [f"共 {len(self.sessions)} 次分析："]
+        for i, s in enumerate(self.sessions, 1):
+            ts = time.strftime("%H:%M", time.localtime(s.timestamp))
+            lines.append(f"  {i}. [{ts}] {s.question}")
+        return "\n".join(lines)
+
+    def clear(self):
+        self.sessions.clear()