MemoryMap_Shutdown deallocated each view, opening holes in the reserved
range, and then released the whole range. A mapping another thread got in
a hole meanwhile was unmapped along with it. On iOS that was Metal's
command buffer memory: headless crashed in vkQueueSubmit about a hundred
frame dumps into a launch. Map inaccessible pages over a released view
instead, so the range stays ours until ReleaseViewSpace.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>