A GPU project whose Render Queue job measured the CPU faster (#3335) rendered
every frame of a batch at once on the CPU, one per thread, with no memory cap:
on a 16-thread machine at about 1.4 GB a frame the app ran out of RAM and
exited without an error (0.23.1, Windows).
While a job renders on the CPU after a GPU frame measured its working memory,
CPU frames in flight now fit half the memory the system has free at that size
per frame, 1 to one per thread, settled once per job and logged. The probe's
timed CPU frames use the same cap. EFFECTCRAFT_CPU_INFLIGHT still overrides
it; Software Rendering projects, with no measurement, are unchanged. The host
reads the free memory through the new JobOptions::free_memory.