feat(plugins): add Sealos

[yangchuansheng]

Summary

• Add Sealos to the Development & Workflow community plugins list
• Mirror the Sealos Codex plugin bundle under plugins/labring/sealos-skills
• Update plugins.json and the local marketplace entry

Validation

• python3 scripts/check-alphabetical.py
• python3 scripts/validate-plugin-pr.py --base-ref origin/main
• python -m json.tool plugins.json
• python -m json.tool .agents/plugins/marketplace.json
• python -m json.tool plugins/labring/sealos-skills/.codex-plugin/plugin.json

Refs labring/sealos-skills#22

[gemini-code-assist]

Code Review

This pull request introduces the 'Sealos Skills' plugin, a comprehensive suite of tools for AI agents to deploy applications to Sealos Cloud. It includes skills for cloud-native readiness assessment, deterministic Docker Compose to Sealos template conversion, and iterative Dockerfile generation, supported by extensive knowledge bases and validation scripts. Feedback was provided on the template converter's fallback logic, which may generate redundant deployment resources when processing Compose files that only contain database services.

[gemini-code-assist]

If the Docker Compose file contains only database services (e.g., just a postgres service), app_services will be empty. The current logic then picks the first service from service_items as the primary app service. This results in generating both a Kubeblocks Cluster and a standard Deployment for the same database image, which is redundant and likely incorrect for Sealos templates. Consider filtering out services already identified as database services when falling back.