test(gguf): Add bfloat16 support to GGUF loading tests

[Rudra-Tiwari-codes]

Proposed changes

This PR extends the GGUF loading tests to support bfloat16 data types. Previously, bfloat16 was missing from the supported_dtypes list in tests/test_load.py, leaving a gap in test coverage for models utilizing this precision format. This change ensures that GGUF save and load operations are correctly validated for bfloat16.

Checklist

Put an x in the boxes that apply.

• [ x] I have read the CONTRIBUTING document
• [ x] I have run pre-commit run --all-files to format my code / installed pre-commit prior to committing changes
• [ x] I have added tests that prove my fix is effective or that my feature works
• [ x] I have updated the necessary documentation (if needed)

[fransafu]

Warning: This author is forking multiple ML projects such as google-deepmind/alphafold, ml-explore/mlx, openai/CLIP, pytorch/pytorch, tensorflow/tensorflow, anthropics/claude-code, vllm-project/vllm, and others, adding minimal "contributions" (often for tests or miscellaneous changes) without proper validation. A review of their commits shows mostly local implementations of TODOs copied from existing projects, with little to no substantive review or testing.

So far, this author has forked 41 repositories following the same pattern. Be careful when accepting this PR. It’s also concerning how this author is able to submit PRs across four repositories in the same day, each requiring large context, which strongly suggests a highly automated workflow.