The instability was not caused by kexec-fiwix logic itself but by oversized early-stage payload pressure in kernel-bootstrap mode.
When too many distfiles are injected before the Fiwix handoff, the early memory/file-table assumptions become fragile and KVM can fail during transition.
This change restores kexec-fiwix.c to the known baseline (matching commit 984b8322...) and fixes the actual failure mode by moving non-early distfiles out of the initial image.
What changed:
- Keep only bootstrap-required distfiles in early init image.
- Generate a separate raw payload image (LBPAYLD1 format) for the remaining distfiles.
- Attach payload image as an extra disk in QEMU/bare-metal kernel-bootstrap flow.
- Add a dedicated C89/tcc-compatible importer (payload-import) that scans payload disks and copies files into /external/distfiles after jump: fiwix.
- Insert improve: import_payload immediately after jump: fiwix so the full distfile set is restored before heavy build steps continue.
- Add PAYLOAD_REQUIRED config gating so this behavior is active only in kernel-bootstrap paths that need it.
Why this design:
- Preserves minimal early environment assumptions (no dependency on full shell utilities for the copy operation itself).
- Avoids adding filesystem-construction toolchain dependencies for the payload container by using a simple length-prefixed raw format.
- Keeps bare-metal and QEMU behavior aligned: both can carry full build artifacts without overloading the early handoff stage.
- Leaves kexec-fiwix behavior deterministic and auditable by reverting to a known-good baseline implementation.
- add --stage0-image in rootfs.py for qemu to boot an existing kernel-bootstrap image
- when --stage0-image is combined with --build-guix-also, update BUILD_GUIX_ALSO in image config and sync /steps-guix into the image
- require stage0 /init to contain guix handoff marker instead of patching /init implicitly
- add run_steps_guix_if_requested() to make_bootable-generated /init so rebooted stage0 images can enter steps-guix directly
- run /steps-guix/0.sh with bash in after.sh
- make script-generator start mode convention-based: /steps stays kaem-first, alternate roots (e.g. /steps-guix) start in bash
- remove redundant explicit /steps config-root argument from seed/preseeded/reconfigure script-generator calls
