fix(internvl): pass max patch count to vllm

[RerankerGuo]

PR type

• Bug Fix
• New Feature
• Document Updates
• More Models or Datasets Support

PR information

Fixes #7631.

Background

InternVL templates read the MAX_NUM environment variable into
template.max_num. The Transformers backend uses this value during
local image preprocessing, but the vLLM branch only emitted the image
placeholder and did not forward the patch limit.

As a result, vLLM used the model configuration's default
max_dynamic_patch, potentially producing prompts that exceeded the
model context even when users set MAX_NUM.

vLLM's InternVL processor accepts max_dynamic_patch through its
multimodal processor kwargs, and VllmEngine already forwards
inputs.mm_processor_kwargs with each request.

Changes

• Forward template.max_num as max_dynamic_patch for InternVL
  templates in vLLM mode.
• Use setdefault so an explicit per-request max_dynamic_patch
  remains authoritative.
• Add CPU tests for default propagation, explicit override precedence,
  and unchanged Transformers behavior.

Verification

• PYTHONPATH=. .venv/bin/python -m unittest tests.general.test_internvl_template
• PYTHONPATH=. .venv/bin/python tests/run.py --pattern test_internvl_template.py
• PYTHONPATH=. .venv/bin/python -m unittest tests.general.test_internvl_template tests.general.test_data_preprocess.TestProviderMessagesPreprocess tests.general.test_data_preprocess.TestRejectedMessagesPreprocess
• .venv/bin/pre-commit run --all-files
• git diff --check

Impact

The change only adds a vLLM multimodal processor kwarg for InternVL
templates. Transformers preprocessing is unchanged. Existing explicit
per-request values are preserved.

Experiment results

Before the fix, the vLLM regression test observed an empty
mm_processor_kwargs dictionary despite max_num=6. After the fix it
contains {"max_dynamic_patch": 6}; all three template tests and ten
related tests pass.

[gemini-code-assist]

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