A user-space display service: owns the write-combining framebuffer, composites a
z-ordered layer stack into a cacheable back buffer, presents only the damaged
region, and is driven over IPC by runtime.display. Proven end to end by the
display-demo client. Kernel changes: a display device node + write-combining
mmio_map, and a page-by-page mmap that lifts the 1 MiB per-call cap. Deferred by
design: shared-memory client surfaces, a native mode-setting backend, and vsync.
Daniel Samson