[Feature]: 基于qwenpaw 2.x的A2A何时支持

## Summary

qwenpaw已经完成了2.x的升级，架构文档中描述MCP/A2A/ACP会通过统一的Driver机制实现。但是当前代码中只支持了MCP，请问，A2A协议后续会官方支持吗？有没有计划时间何时完成？

## Component(s) Affected

- [x] Core / Backend (app, agents, config, providers, utils, local_models)
- [ ] Console (frontend web UI)
- [ ] Channels (DingTalk, Feishu, QQ, Discord, iMessage, etc.)
- [ ] Skills
- [ ] CLI
- [ ] Documentation (website)
- [ ] Tests
- [ ] CI/CD
- [ ] Scripts / Deploy

## Problem / Motivation

当前无官方的A2A协议支持，无法接入多Agent（尤其是外部Agent）协同。

## Proposed Solution

官方基于Driver机制实现A2A

## Alternatives Considered

官方or社区提供A2A插件。

## Additional Context

None

## Willing to Contribute

- [x] I am willing to open a PR for this feature (after discussion).

Start by reading the architecture documentation and the existing MCP implementation built around the unified Driver mechanism. Confirm the intended A2A scope, integration points, compatibility expectations, and tests needed; done means A2A support is implemented through that Driver mechanism and verified for external multi-agent collaboration.

索引モデルが issue の本文から書いたものです。