feat: fix feishu channel reload failed

[rayrayraykk]

Description

[Describe what this PR does and why]

Related Issue: Fixes #(issue_number) or Relates to #(issue_number)

Security Considerations: [If applicable, e.g. channel auth, env/config handling]

Type of Change

• Bug fix
• New feature
• Breaking change
• Documentation
• Refactoring

Component(s) Affected

• 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

• 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)
• 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]

[Copilot]

Pull request overview

This PR addresses Feishu channel reload/shutdown stability by making the WebSocket client run on a per-thread event loop and adding cleanup/guards to avoid using a closed loop during reload.

Changes:

• Track a dedicated WebSocket thread event loop (_ws_loop) and restore lark_oapi.ws.client.loop after the thread exits.
• Add a _closed flag to drop incoming WS messages during shutdown.
• Update stop() to stop the WS event loop and add a warning when the WS thread does not terminate within the timeout.

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