Add a new "builder" capability to trigger Nix builds on a dedicated
build host via NATS messaging. This allows pre-building NixOS
configurations before deployment.
New components:
- Builder mode: subscribes to build.<repo>.* subjects, executes nix build
- Build CLI command: triggers builds with progress tracking
- MCP build tool: available with --enable-builds flag
- Builder metrics: tracks build success/failure per repo and host
- NixOS module: services.homelab-deploy.builder
The builder uses a YAML config file to define allowed repositories
with their URLs and default branches. Builds can target all hosts
or specific hosts, with real-time progress updates.
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
