Release ContentCloud v0.9.0

[wutongci]

Summary

• add a unified Agent Client Registry with explicit available/planned capabilities
• add generic project and review-feedback Agent handoff contracts with a Codex strategy and compatibility layer
• converge bootstrap, workspace registration, automation, and environment harness validation on the registry
• add fail-closed Plugin upgrade/resume behavior and publish version 0.9.0 across CLI, Web, npm launcher, Plugin, MCP, and environment metadata

Validation

• pnpm install --frozen-lockfile
• make check
• go test -race ./...
• Web tests: 50 passed
• Plugin deterministic evaluation: 11 scenarios passed
• six-platform CLI cross-build with gzip and SHA-256 verification

Deployment

• no database migrations
• native systemd Server/Worker deployment remains unchanged
• malware scanning remains disabled; no ClamAV tooling is introduced