Fix/sqlite cascade delete issue

[Gui-Yue]

Summary

修复 SQLite 存储中 INSERT OR REPLACE 导致的外键级联删除问题：更新 Agent
元数据时，messages、tool_calls、snapshots 子表数据被意外清空。

• Close When using sqlite for store, the messages, tool_calls cannot be persisted, only agents data can be saved #49

Motivation / Context

SqliteStore.saveInfo() 使用 INSERT OR REPLACE INTO agents，在 SQLite 中等价于 DELETE + INSERT。由于子表声明了 FOREIGN KEY ... ON DELETE CASCADE，每次更新 agent 信息都会触发级联删除，导致关联的 messages、tool_calls、snapshots 全部丢失。

修复方式：将 INSERT OR REPLACE 改为 INSERT ... ON CONFLICT DO UPDATE SET（UPSERT），避免触发
DELETE；同时启用 PRAGMA foreign_keys = ON 使外键约束生效。

Type of Change

• Bug fix
• Feature
• Refactor
• Docs
• Test
• Chore / Build

Scope / Modules

• core (agent / events / pool / room / scheduler)
• infra (db / provider / sandbox / store)
• tools (fs / bash / mcp / skills / task)
• skills
• examples
• docs (en / zh-CN)
• tests
• other: ___

Public API

• Exports changed in src/index.ts
• No public API change

Breaking Changes

• Yes , and attach report(include necessity) and transition plan
• No

Testing

• npm run test:unit(required)
• npm run test:integration(if needed)
• npm run test:e2e(if needed)

Impact / Risk

风险较低。

本次改动：

• saveInfo() 和 saveSnapshot() 从 INSERT OR REPLACE 改为 ON CONFLICT DO UPDATE，语义不变，仅避免触发 DELETE 行为。
• 新增 PRAGMA foreign_keys = ON，使外键约束（含 delete() 方法的级联删除）正确生效。
• 新增回归测试验证更新 agent 后子表数据完整性。

Checklist

• Docs updated if needed
• Examples updated if needed
• New feature includes related tests and docs
• Tests follow tests/README.md structure
• Docs follow docs/en + docs/zh-CN format rules
• No secrets or tokens committed
• No dist/ changes (unless release)
• Only one lockfile updated for the package manager used