Motion key errors with oriented curves and motion blur

**Describe the bug**
If you have motion blur and oriented curves, you get this ERROR:

`ERROR | [curves] /root/curves/curve_0: orientations must have the same number of motion keys as points (found 1, expected 2)`

**To Reproduce**
Steps to reproduce the behavior:
1. Extract [curves.zip](https://github.com/user-attachments/files/20931301/curves.zip)
2. kick the usd file, or load it into Houdini and render

**Used Software Versions**
- Arnold: 7.4.2.1

Extract curves.zip and load the USD file in Houdini, then render it with Arnold 7.4.2.1 to reproduce the motion-key error. Trace the oriented-curve handling involved in motion blur; done means the scene renders without the reported orientation and motion-key mismatch.

Written by the indexing model from the issue text.