feat: 基于 Skills + 沙箱 + 数据库存储构建自动代码评审 Agent

[Stelquis]

基于 tRPC-Agent 框架构建的自动代码评审 Agent，集成 Skills、沙箱执行、Filter 治理、数据库存储和监控审计能力。输入 git diff / PR patch / 本地变更，通过 code-review Skill 加载规则，经 Filter 前置拦截后进入沙箱执行检查，发现问题结构化输出并落库持久化。
新增 examples/skills_code_review_agent/ 目录，包含：

• 9 个核心模块（输入解析/沙箱/脱敏/Filter/去重/报告/监控/配置/CLI）
• CR Skill（SKILL.md + 5 类规则文档 + 3 个沙箱脚本）
• 数据库层（5 张表 + StorageABC 抽象接口 + SQLite 实现）
• 主入口 review_agent.py + 干跑模式 dry_run.py
• 8 条测试样本 + 示例报告 + 使用说明 + 方案设计说明

关联 Issue: #92

[codecov]

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