An 18-byte DTD with fixed reduced blanking (80 px / 45 lines — a virtual display's blanking only has to be self-consistent), refusing modes the encoding cannot carry (pixel clock past the u16 10 kHz field, 4K120-class; >12-bit actives). Lives here rather than in the driver so it is unit- tested on every platform; pf-vdisplay splices it over its hard-coded 1080p60 preferred-timing descriptor. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>