Only Hera writes the shared physical timer period now, gated by
vm_uuid_is_hera(vm->stadium_vm_id) in vm_tick_inference_engine(). Every
other VM's Loop #7 still adapts its own tick_target_ns as before, it just
no longer races to re-arm the one physical timer.
Includes 3-arch acceptance run (amd64/aarch64/riscv64, all booted clean
to ok>) and regenerated capsule/DoE artifacts.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
