Fix gpt oss weight loading with EP + bf16

[ashors1]

Purpose

The signature for _load_weights_other is incorrect. The start and end indices are flipped, which casues an indexing issue when attempting to extract the weights on the current EP rank. This fixes the signature to be consistent with _load_weights_mxfp4.

Test Plan

Test Result

Running _load_weights_other with EP now works as expected.

---

Essential Elements of an Effective PR Description Checklist

• The purpose of the PR, such as "Fix some issue (link existing issues this PR will resolve)".
• The test plan, such as providing test command.
• The test results, such as pasting the results comparison before and after, or e2e results
• (Optional) The necessary documentation update, such as updating supported_models.md and examples for a new model.
• (Optional) Release notes update. If your change is user facing, please update the release notes draft in the Google Doc.

[gemini-code-assist]

Code Review

This pull request correctly identifies and fixes a bug in the _load_weights_other method within the GptOssModel class. The parameters ep_rank_start and ep_rank_end were swapped in the function signature, leading to incorrect weight slicing when using expert parallelism. The change aligns the signature with its call site and makes it consistent with the _load_weights_mxfp4 method, resolving the indexing issue. The fix is accurate and well-contained.

[jikunshang]

nice catch! thanks for fixing.