Rework the release workflow from a single x86_64 build into a matrix that
builds x86_64 (bootable image), aarch64 and armv8i (bare-metal kernel ELFs)
in parallel, then publishes one prerelease carrying every architecture's
artifacts plus a combined SHA256SUMS.
- x86_64 builds natively (build-essential + nasm + rustc, CROSS_COMPILE=),
matching the validated local toolchain; aarch64/armv8i use the apt cross
compilers (gcc-aarch64-linux-gnu, gcc-arm-linux-gnueabihf).
- Artifacts are named SUB-OS-<tag>-<arch>-... and collected by a release job.
- Notes refreshed for the GUI desktop and multi-arch support.
Co-Authored-By: Claude Opus 4.8 <[email protected]>
Claude-Session: https://claude.ai/code/session_01Fh5z6V7nGPbHvqVG5p4CXX
