Delete HF version of Phi 4 MM

[hmellor]

Phi 4 multimodal is currently compatible with vLLM in 2 ways:

• Phi4MMForCausalLM - reimplemented in vLLM based on Microsoft's custom code from https://huggingface.co/microsoft/Phi-4-multimodal-instruct
• Phi4MultimodalForCausalLM - reimplemented in vLLM based on Huigging Face Transformers (requires https://huggingface.co/microsoft/Phi-4-multimodal-instruct/discussions/70)

Given that:

• Microsoft appears to have no intention of merging the PR
• The PR for the Transformers version is no longer compatible with vLLM on the latest Transformers (v5)

We have decided to drop support for the Transformers implementation in vLLM.

This means that:

• Using Phi 4 multimodal in vLLM will always require --trust-remote-code
• Phi 4 multimodal will eventually become incompatible with vLLM as its custom code rots

[mergify]

Documentation preview: https://vllm--30049.org.readthedocs.build/en/30049/

[gemini-code-assist]

Code Review

This pull request removes support for the Hugging Face Transformers version of the Phi 4 multimodal model (Phi4MultimodalForCausalLM). The changes are consistent and well-executed, covering the model implementation, its registration in various registries, associated tests, and documentation. The removal is clean and complete within the scope of the provided files, with no apparent dangling references. Overall, this is a solid cleanup effort.

[DarkLight1337]

cc @Isotr0py

[hmellor]

Sorry @Isotr0py, I know you put a lot of work into this implementation 😢

[Isotr0py]

BTW, I wonder if we can create a separated community repo like mistral-community/pixtral-12b/deepseek-community/deepseek-vl-7b-chat to hold HF format model instead of converting existing repo?

[hmellor]

Good suggestion, we'll make a community repo so that at least the Transformers implementation is usable in Transformers without needing to specify a ref.