feat(adapter): add Codex MCP gateway bridge

[WHUTcjh-2024]

Description | 描述

Add a focused STDIO MCP adapter that exposes the existing TDAI Gateway to
Codex and other MCP clients. The adapter remains a transport boundary; storage,
ranking, capture, and pipeline behavior stay in the existing memory engine.

Adapter capabilities

• Publish an executable memory-tencentdb-mcp npm command.
• Implement the latest published MCP revision (2025-11-25) and negotiate
  2025-06-18, 2025-03-26, and 2024-11-05 clients.
• Enforce the MCP initialization lifecycle, integer/string request IDs, closed
  tool schemas, runtime rejection of extra arguments, notifications, parse
  errors, and MCP tool-error semantics.
• Expose five tools: recall, capture, L1 memory search, L0 conversation search,
  and session flush.
• Call the Gateway through an authenticated, timeout-bounded HTTP client that
  preserves base paths, validates object responses, and rejects ambiguous or
  credential-bearing URLs.
• Reserve STDOUT for newline-delimited MCP JSON-RPC frames and send fatal
  startup diagnostics to STDERR.

Recall compatibility

The Gateway now returns prepend_context and append_system_context
separately so MCP hosts do not flatten dynamic and stable prompt content. The
legacy context field keeps its original meaning for existing clients.

Documentation

The adapter guide includes architecture, security boundaries, all five tools,
environment variables, and a Codex config.toml example verified against the
official mcp_servers.<id> configuration reference.

Related Issue | 关联 Issue

Closes #235

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

Validation

• Node.js 24: 7 test files, 95 tests passed.
• MCP/Gateway coverage includes lifecycle negotiation, all tools, strict input
  validation, parse errors, tool errors, timeout/network failures, real local
  HTTP routing, Bearer authentication, and response-shape validation.
• npm run build: passed; generated executable MCP bundle is about 14.4 KB.
• npm pack --dry-run --json: passed and includes the MCP binary and guide.
• git diff --check: passed.

The current Gateway scopes memory by session_key. This adapter does not claim
user_id as a tenant-isolation boundary because the core storage path does not
yet enforce that scope.

[Maxwell-Code07]

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