rgbd: avoid unaligned SIMD stores in LineMOD

[Nikhi00718]

Summary

• avoid aligned SIMD destination accesses when LineMOD response-map rows are not 16-byte aligned
• retain the aligned path only when both source and destination row strides preserve alignment
• add a regression test using a 218-pixel, 3-channel image

Fixes #29559

Testing

• git diff --check
• The native OpenCV C++ test suite could not be built in this Windows environment because no C++ compiler is installed. The added rgbd regression test is intended to run in repository CI.

AI assistance disclosure

I identified and reproduced the issue, then used OpenAI Codex to assist with the implementation and regression-test work. I personally reviewed the resulting diff and ran the validation commands listed above to verify the fix. Any full-suite or local-environment limitations are documented in the validation section.

[Nikhi00718]

I reviewed the SIMD change: the aligned path is now selected only when both source and destination base addresses and row strides preserve 16-byte alignment, while unaligned loads/stores cover the fallback. The added 218-pixel, 3-channel regression targets the reported row-stride case. Native rgbd CI is still required because this host has no C++ build toolchain; please request maintainer review on the current head.