Two DRM drivers coexist in one illumos kernel — a graphics prerequisite, proven

A modern laptop needs two DRM drivers in one kernel (the X1 has an Intel iGPU and an NVIDIA dGPU), and ports of the OpenBSD drm stack make that dangerous: each compat layer exports the same ~870 OpenBSD-kernel-API symbol names, and illumos's kernel linker (krtld) binds the second module's references to the first module's copies, silently cross-wiring two unrelated drivers. We fixed it structurally — each compat layer is scoped so only the real module interface (_init, _fini, _info, _depends_on) is global and every compat symbol is module-local. Measured on the X1: before, iwm exported 871 globals and i915 4643, sharing 33 non-interface names; after, 3 and 4, sharing zero. A permanent build gate fails if either driver ever leaks a non-interface global again. Proven live: the iwm wifi driver and the i915 GPU driver loaded into one running kernel at the same time, with wifi still scanning while the GPU driver was resident — no cross-wiring, no panic. This is explicitly a prerequisite, NOT graphics working: the i915 driver loads and coexists, but it does not yet own the display. On illumos the boot console driver holds the GPU's device node with no live-handover protocol, and a review of a recovered console-handover implementation found it both unsafe and ineffective, so it was not adopted. A safe console handover must be written before an i915 attach yields a usable graphical console — that is the current gate for a desktop on this hardware, and COSMIC is downstream of it.