fix: exclude broken transformers release

[kmishra1204]

Fixes #10610

The issue thread identifies transformers==5.6.0 as the broken release for the FlashAttention path, and maintainers noted that upgrading Transformers avoids it.

This updates the supported Transformers spec in both install metadata and the runtime dependency check:

• allow <=5.7.0
• keep the existing !=4.57.0 exclusion
• add !=5.6.0 so existing broken environments fail the version gate instead of passing silently

Validation:

• uvx ruff check pyproject.toml src\llamafactory\extras\misc.py
• py -m py_compile src\llamafactory\extras\misc.py
• git diff --check

[gemini-code-assist]

Code Review

This pull request updates the transformers dependency constraints in pyproject.toml and src/llamafactory/extras/misc.py to support versions up to 5.7.0 while excluding 4.57.0 and 5.6.0. Feedback highlights that passing multiple inequality constraints (like !=4.57.0 and !=5.6.0) in a single requirement string to check_version will cause the earlier exclusion to be silently overwritten due to Hugging Face's internal version parsing implementation, and suggests splitting them into separate calls.

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[gemini-code-assist]

Due to an implementation detail in Hugging Face's transformers.utils.versions.require_version, passing multiple version constraints with the same operator (such as !=4.57.0 and !=5.6.0) in a single requirement string will result in the earlier constraints being silently overwritten.

Specifically, require_version parses the requirement string and stores the operators in a dictionary keyed by the operator itself (wanted[op] = want_ver). Because of this, wanted["!="] will only retain the last exclusion (5.6.0), and the !=4.57.0 check will be completely ignored at runtime.

To prevent this, we should split the checks into separate check_version calls.

Suggested change

	check_version("transformers>=4.55.0,<=5.7.0,!=4.57.0,!=5.6.0")
	check_version("transformers>=4.55.0,<=5.7.0")
	check_version("transformers!=4.57.0")
	check_version("transformers!=5.6.0")

[kmishra1204]

Updated after the review note.

Change made:

• Kept the package metadata constraint as one PEP 508 requirement.
• Split the runtime dependency checks into separate check_version(...) calls for the range and each excluded Transformers release, so !=4.57.0 and !=5.6.0 are evaluated independently.

Validation rerun:

• uvx ruff check pyproject.toml src\llamafactory\extras\misc.py - passed
• py -m py_compile src\llamafactory\extras\misc.py - passed
• AST sanity check confirmed runtime checks for transformers>=4.55.0,<=5.7.0, transformers!=4.57.0, and transformers!=5.6.0
• git diff --check - passed