Extraction finished clean (73 GB). The editor crashed twice with signal 11, but
the log named the real cause: the agent shell's home is read-only, so the editor
could not create ~/.config/Epic and died in pre-init. With HOME redirected it
reaches 'Engine is initialized' under -NullRHI, proving the install and bundled
libraries are sound on Bazzite.
The Vulkan RHI is still unproven: the successful run used -NullRHI. A desktop
terminal run is the remaining step, recorded in Docs/environment.md, ROADMAP and
the toolchain pin.