Introduce the forge-builder crate that automatically delegates builds to
an ephemeral VM when the host can't build locally (e.g., QCOW2 targets
without root, or OmniOS images on Linux). The builder detects these
conditions, spins up a VM via vm-manager with user-mode networking,
uploads inputs, streams the remote build output, and retrieves artifacts.
Key changes:
- New forge-builder crate with detection, binary resolution, VM lifecycle
management, file transfer, and miette diagnostic errors
- BuilderNode added to spec-parser schema for per-spec VM config
- --local and --use-builder CLI flags on the build command
- Feature-gated (default on) integration in forger CLI
- Fix ext4 QCOW2 grub-install failure by using absolute paths in chroot
- Improve debootstrap to pass --components and write full sources.list
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
