release: v0.27.0

[wutongci]

Summary

• release ContentCloud v0.27.0
• add Seedance 2.5 provider integration, prompt package validation, cancellation and reconciliation
• add ContentCloud Marketing Skill Pack and governed plugin metadata
• update CLI, Server, Worker, Web, plugins, MCP, environment profile and documentation

Validation

• make check
• go test -race ./...
• pnpm --dir web test
• pnpm --dir web typecheck
• pnpm --dir web build
• node --check packages/contentcloud/bin/contentcloud.js
• plugin release validation and evaluation
• marketing plugin validation