nikon_he: complete HE/HE* header parsing and integration - #1

Builds on LibRaw#826 by @yogthos. The original three commits and authorship are preserved; this PR contains only the follow-up changes.

Changes:

• parse the JPEG XS picture header and derive GTLI from the per-file WGT marker
• dispatch HE/HE* using Nikon's MakerNote compression value
• validate the fixed Nikon profile and harden short-read/error paths
• add the new parser to the supported build configurations

Validation:

• full MinGW static-library build
• six HE/HE* samples from Z 9, Z 8, and Z f
• header truncation, bit-flip, random-input, and unsupported-profile tests
• git apply --check against Add Nikon Z9 High-Efficiency (HE) RAW format support LibRaw/LibRaw#826 head 8aebd05

Known limits:

• all errors larger than 1 LSB are confined to the final two image rows; the Adobe boundary convention is still unresolved
• DX crop and ZR samples have not been validated
• MSVC project files were syntax-checked but not built

AI assistance was used during implementation and review. I reviewed and tested the resulting code and take responsibility for the contribution.

I agree that this contribution may be distributed under both LGPL 2.1 and CDDL 1.0.