Iterate the sysroot/rootfs build plan (in-container)

Treat the build plan JSON as immutable during iteration. Use the overrides file for “what should be back-annotated later”, and use the state file for “where am I in this run”.

Canonical paths (inside the rootfs)

• Plan (immutable): /var/lib/sysroot-build-plan.json
• Overrides (mutable, back-annotate later): /var/lib/sysroot-build-overrides.json
• State/bookmark (mutable, auto-updated): /var/lib/sysroot-build-state.json
• Failure reports (append-only): /var/lib/sysroot-build-reports/*.json

Source trees:

• Live repo (mutable, preferred for iteration): /work/bootstrap-qcow2
• Staged snapshot (static, produced by sysroot-builder): /workspace/bootstrap-qcow2-master

Minimal iteration loop