docs: lab platform design — labd, agent, RBAC, multi-cloud, testing strategy
Comprehensive design document covering:
- labd master daemon with CA, RBAC, Pulumi executor
- lab-agent with mTLS enrollment, heartbeat, log shipping
- Module system (built-in + external repos)
- Cloud/environment model (baremetal + AWS)
- Ephemeral test environments (containers, VMs, cloud)
- Security test patterns for RBAC
- Health gates for deployment promotion
- Database strategy: PostgreSQL now, CockroachDB later
- Networking: Tailscale mesh + Cilium CNI
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>