feat(core): expose direct memory write tool

[RerankerGuo]

Description | 描述

Expose a new tdai_memory_write tool for explicit long-term memory writes from agent/subagent contexts.

• Adds a store-only memory write helper that appends L1 records and optionally dual-writes to the vector store.
• Registers tdai_memory_write with content, type, and scene_name parameters.
• Adds focused coverage for successful writes and validation errors.

Related Issue | 关联 Issue

Fix #66

Change Type | 修改类型

• Bug fix | Bug 修复
• New feature | 新功能
• Documentation update | 文档更新
• Code optimization | 代码优化

Self-test Checklist | 自测清单

• Verified locally | 本地验证通过
• No existing features affected | 无影响现有功能

Additional Notes | 其他说明

Verified with npx vitest run src/core/tools/memory-write.test.ts, npm test, and npm run build using Node v24.15.0.