Reduce the control plane's dependency on helper scripts while keeping the hard Linux integration points in the approved shell-out layer.
Replace the bash-driven image build path with a native Go builder that clones and optionally resizes the rootfs, boots a temporary Firecracker VM, provisions the guest over SSH, installs packages and modules, and preserves the package-manifest sidecar.
Also replace a few small convenience shell-outs with Go helpers: read process stats from /proc, use os.Truncate for ext4 image growth, add file-clone and normalized-line helpers, drop the sh -c work-disk flattening path, and launch Firecracker via a direct sudo command.
Add tests for the new SSH/archive and system helpers, plus a policy test that keeps os/exec imports confined to cli/firecracker/system. Update the docs to describe customize.sh as a manual helper rather than the daemon's image-build backend.
Validated with go mod tidy, go test ./..., and make build.
Dangerous lifecycle, store, system, and RPC paths still had little or no automated confidence, and the live smoke harness failed opaquely when guest boot timing drifted. This adds targeted unit coverage for store allocation and decode failures, system helper failure ordering and cleanup, RPC error handling, and daemon lookup/reconcile/editing/stats/preflight edge cases.
It also makes verify.sh wait for daemon-observable VM readiness before SSH, reuse a bounded boot deadline for the SSH phase, and dump VM metadata, logs, tap state, socket state, and NAT rules on timeout so host-level failures are diagnosable instead of surfacing only connection refused.
Validation: go test ./..., go test ./... -cover, bash -n verify.sh. No live ./verify.sh boot was run in this environment.
