According to Contax literature specs, their 45mm Planar is actually 47mm focal length.
The Minolta CLE is a favorite of mine, and I have two. I have not made a formal comparison of the framing accuracy, but of course it changes with focus distance since the framelines are fixed in size. At the “usual” distances, say 2 yards to 10 yards, my sense is that the frames are usefully close to accurate with the 40mm Rokkor.
I also have used the Voigtlander 1.4/40mm Nokton on the CLE and note that the framelines are a bit generous for it. Seems the Nokton has a slightly longer focal length / smaller field of view than the Rokkor. I have tended to use the inside edges of the frames with that lens. Similarly, I’ve also used the Pentax 1.9/43mm SMCP on the camera with similar conservative use of framelines.
I would expect the Planar’s 47mm focal length to have a field coverage well within the CLE framelines maybe even at infinity. I have that lens too, and it's a gem. But the Rokkor is also a gem - so is the Pentax Special - and IMO either is a more attractive and convenient option than converting the Planar.