feat(tool): execute_shell_command encoding on Windows

[snai1557]

Description

#979

之前合并的代码漏了一处没有处理.

Type of Change

• [ x ] Bug fix
• New feature
• Breaking change
• Documentation
• Refactoring

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

Checklist

• [ x ] I ran pre-commit run --all-files locally and it passes
• If pre-commit auto-fixed files, I committed those changes and reran checks
• I ran tests locally (pytest or as relevant) and they pass
• Documentation updated (if needed)
• [ x ] Ready for review

Testing

[How to test these changes]

Local Verification Evidence

pre-commit run --all-files
# paste summary result

pytest
# paste summary result

Additional Notes

[Optional: any other context]

[gemini-code-assist]

Warning

You have reached your daily quota limit. Please wait up to 24 hours and I will start processing your requests again!

[xieyxclack]

LGTM