I'm installing a sub-panel in a rec room. I know the NEC states
clearance in front of the panel needs to be 30" wide and 36" deep.

From where is that 30" wide measured? Is it on-center with the panel,
or can it be from one edge of the panel? My optimal location puts the
panel in a corner, which means one edge of the panel is up against a
perpendicular wall. As long as I have 30" clearance in front of the
panel measured from that perpendicular wall, is it OK?

It is new & permitted construction, so the AHJ will need to inspect.

Mike