[Bugfix] Fix multimodal configuration for Qwen3VL MOE model

[maxyanghu]

Purpose

After #29752 enabled Efficient Video Sampling for Qwen3VLForConditionalGeneration model, Qwen3VLMoeForConditionalGeneration model errors out due to newly added configuration is_multimodal_pruning_enabled not initialized and set.

This PR fixes the issue and set the field.

Test Plan

vllm serve RedHatAI/Qwen3-VL-235B-A22B-Instruct-NVFP4 --async-scheduling --max-model-len 32768 --max-num-seqs 1024

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[mergify]

This pull request has merge conflicts that must be resolved before it can be
merged. Please rebase the PR, @maxyanghu.

https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/working-with-forks/syncing-a-fork

[gemini-code-assist]

Code Review

This pull request correctly fixes a bug in the Qwen3VLMoeForConditionalGeneration model where the is_multimodal_pruning_enabled attribute was not being initialized. This led to an error when using the model with multimodal configurations that enable video sampling. The change adds the necessary initialization, resolving the issue. The fix is correct and directly addresses the problem described.

[DarkLight1337]

Oops, thanks for fixing!

[DarkLight1337]

Can you resolve the merge conflict?

[DarkLight1337]

There is still a merge conflict

[maxyanghu]

There is still a merge conflict

All conflict should be resolved now. This is a quick fix but I feel like this class needs refactoring. Qwen3VLMoeForConditionalGeneration(sub class) and Qwen3VLForConditionalGeneration (base class) has lots of duplicated code in __init__