Boot flow-kernel on Android through Termux QEMU

[godofecht]

Adds a reproducible Android boot path for the current x86_64 Multiboot2 kernel without modifying the Android bootloader or host kernel.

The new Termux setup helper installs the current qemu-system-x86-64 package, while android/termux-run.sh boots the existing flow-kernel.iso under QEMU TCG with serial output only.

Kernel CI validates the Android scripts, builds the freestanding kernel against current flow/main, builds the GRUB ISO, boots the kernel through the same Android-compatible runner, asserts Flow kernel: entry and Flow kernel: boot contract accepted, and publishes a flow-kernel-android-x86_64 artifact containing the ISO, setup helper, runner, documentation, and SHA-256 manifest.

This also repairs pre-existing CI/compiler drift: Flow dependency setup is rooted at the checked-out compiler, generated C is kept freestanding with a minimal libc compatibility surface, privileged x86 helpers are separated from @cEmbed, required GRUB image tooling is installed, and ELF inspection uses tools present on the runner.

CI run 32430467004 is green end to end.

This intentionally keeps the existing x86_64 kernel unchanged at the boot-contract level. A native aarch64 QEMU virt target can follow separately.

[godofecht]

This branch is green, but it targets the retired bespoke x86_64 Multiboot2 architecture and would reintroduce an obsolete roadmap into the README. The Android VM objective is preserved in #3, rebuilt on the repo's canonical Tiny Core/Linux substrate from #1. Closing this draft as superseded rather than merging stale architecture.