fix(qwen3_moe): correct return type annotation on Qwen3MoeSparseMoeBlock.forward

[RudrenduPaul]

What does this PR do?

Corrects an incorrect return type annotation on Qwen3MoeSparseMoeBlock.forward.

The method is annotated as returning tuple[torch.Tensor, torch.Tensor] but actually returns a single reshaped torch.Tensor (see the return final_hidden_states.reshape(...) statement). This type mismatch was identified in issue #45208 and confirmed by maintainer @Rocketknight1.

Fixes #45208

Changes

• src/transformers/models/qwen3_moe/modular_qwen3_moe.py: Fix return type annotation from tuple[torch.Tensor, torch.Tensor] to torch.Tensor
• src/transformers/models/qwen3_moe/modeling_qwen3_moe.py: Same fix in the generated file (kept in sync with the modular file)

Tests

No functional change — annotation-only fix. Existing tests continue to pass.

This is not a duplicate of PR #45211 (which was opened and closed without review before the maintainer commented on the issue).

Note: This PR was developed with AI assistance (Claude Code). I have reviewed every line and understand the change.

[Rocketknight1]

@RudrenduPaul can you run make fix-repo to clean up any modular/modeling issues and propagate the fix, then ping me for final review? Thank you!

[RudrenduPaul]

Hi @Rocketknight1 — ran make fix-repo (using python3 utils/checkers.py directly since the python alias wasn't available). All the key consistency checks passed with no changes needed:

✅ auto_mappings — OK
✅ doc_toc — OK
✅ copies — no # Copied from drift detected
✅ modular_conversion — no generated-file divergence
✅ dummies — OK
✅ pipeline_typing — OK

(3 checks failed due to missing local packages — ruff, gitpython, setuptools — these are env setup issues on my machine, not repo inconsistencies.)

The branch is also up to date with main (the upstream sync from the 'Update branch' button is already included). Ready for your final review whenever you're free — thanks!

[RudrenduPaul]

@Rocketknight1 — follow-up on the check_repository_consistency failure.

The CI diff showed the modular conversion of Qwen3VLMoeTextSparseMoeBlock and Qwen3OmniMoeThinkerTextSparseMoeBlock (both inherit from Qwen3MoeSparseMoeBlock via pass) would generate -> torch.Tensor, while the actual generated modeling files still had -> tuple[torch.Tensor, torch.Tensor].

Just pushed a second commit propagating the fix to:

• modeling_qwen3_vl_moe.py — Qwen3VLMoeTextSparseMoeBlock.forward
• modeling_qwen3_omni_moe.py — Qwen3OmniMoeThinkerTextSparseMoeBlock.forward

(Left Qwen3OmniMoeTalkerTextSparseMoeBlock untouched — it inherits from Qwen2MoeSparseMoeBlock, not Qwen3.)

Should be ready for final review now!

[github-actions]

[For maintainers] Suggested jobs to run (before merge)

run-slow: qwen3_moe, qwen3_omni_moe, qwen3_vl_moe

[Rocketknight1]

Yep, LGTM now!

[HuggingFaceDocBuilderDev]

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