Fix Windows NIfTI paths and release dcccpy 0.1.7

[tctco]

Summary

• preserve full ASCII filenames on Windows so ITK continues to see compound .nii.gz extensions instead of an 8.3 .GZ path
• update slim dcccpy to 0.1.7 and its default DCCCcore download to 4.3.0
• add dcccpy.pet_motion_correct() with corrected-dynamic and motion TSV options
• update runtime packaging documentation and tests

Context

The initial v4.3.0 tag workflow built successfully on Linux x64/ARM and both macOS runners. Windows compiled and installed successfully, but three PET motion-correction tests failed because GetShortPathNameW changed .nii.gz inputs to .GZ, preventing ITK from selecting NiftiImageIO. No GitHub Release was created.

Verification

• Docker incremental Release build: passed
• PET motion correction and Unicode path tests: 4 passed, 2 skipped
• dcccpy tests: 13 passed, 1 skipped
• dcccpy wheel and sdist: built successfully
• twine check: passed
• clean wheel install: version 0.1.7, DCCCcore 4.3.0, helper exported