PCB AI skips a second PDF exam (pintable cache, pdf_path=None) and the report
gains a PCB exam section plus power-trace, thermal, via, Kelvin, and GND-stitch
checks grounded in board geometry and extracted specs.
Documents a parallel MODE=pcb exam job (inventory + datasheet-gated
checks) that reuses placement_check, si_check, and the placement job
pattern. Parks F2 packing/export.