feat(wechat-archive): add archive export CLI and local archive tooling

[redyuan43]

Summary

• add WeChat archive export and analysis tooling plus the wechat-archive skill
• add local embedding and rerank example servers and helper scripts
• harden semantic processing and embedding truncation fallback for archive workloads

Testing

• not run locally in this flow

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}

[github-actions]

Failed to generate code suggestions for PR