Generate motion reference and run motion correction. - [x] Create `src/rbc/core/functional/motion.py` - [x] `generate_motion_reference()`: extract middle volume - [x] `motion_correction()`: FSL mcflirt with reference - [x] Unit test for middle volume logic - [x] Integration test with 10 volumes (~1 min) - [x] Full test marked as slow (~5 min) **Outputs:** `sbref`, `desc-motion_bold`, `desc-movementParameters_motion`, motion matrices **Reference:** [Step 7: Motion Reference](https://github.com/childmindresearch/rbc/blob/main/rbc_reimplementation_guide.md#step-7-motion-reference-generation) and [Step 8: Motion Correction](https://github.com/childmindresearch/rbc/blob/main/rbc_reimplementation_guide.md#step-8-motion-estimation-and-correction-mcflirt)
Generate motion reference and run motion correction.
src/rbc/core/functional/motion.pygenerate_motion_reference(): extract middle volumemotion_correction(): FSL mcflirt with referenceOutputs:
sbref,desc-motion_bold,desc-movementParameters_motion, motion matricesReference: Step 7: Motion Reference and Step 8: Motion Correction