Fix/minicpmv46 missing version

[wjinxu]

Reported in OpenBMB/MiniCPM-V#1113 (vllm serve openbmb/MiniCPM-V-4_6).

Fix

Two layers:

1. MiniCPMV4_6ProcessingInfo.get_hf_processor() now returns the native MiniCPMV4_6Processor directly instead of the vendored wrapper. MiniCPM-V 4.6 already implements its own image/video handling and prompt-update logic, so it neither needs nor is compatible with the vendored processor designed for 2.x/4.0/4.5. The transformers v5+ image_mean/image_std ndarray→list normalization is preserved.

2. Defensive safety net: MiniCPMVProcessor.__init__ reads getattr(image_processor, "version", None) instead of hard-crashing, so any future MiniCPM image processor that drops version degrades gracefully. version is only used to special-case the 2.5 tokenization path; any other value already takes the default branch.

Test Plan

Verified end-to-end with vllm serve on transformers 5.9.0 (a true v5 env), image+text request to each:

Version	Arch	Startup	Image+text result
2.5 (MiniCPM-Llama3-V-2_5)	MiniCPMV	OK	correct
4.5 (MiniCPM-o-4_5)	MiniCPMO	OK	correct
4.6 (MiniCPM-V-4_6)	MiniCPMV4_6	OK	correct

The 4.6 run confirms the original AttributeError is gone; 2.5/4.5 confirm the vendored path is unaffected.

Fixes OpenBMB/MiniCPM-V#1113

cc @DarkLight1337 @tc-mb

[tc-mb]

Yes, when merging #44282 before, it wasn't fully tested.
This PR will fix and add the missing parts. Sorry for the inconvenience.

[wjinxu]

@DarkLight1337 The docs/readthedocs.org:vllm red is stale, not a real docs failure.

That RTD build (#33053507) ran before the ready label was added: its post_checkout step runs docs/pre_run_check.sh, which polled pre-commit/pre-run-check, saw it failing (the label/merge-count gate), and skipped the docs build, exiting 1 — mkdocs never actually ran. After the label was added the gate passed and buildkite re-ran green, but RTD doesn't auto-rebuild the same commit, so its status is frozen on that pre-label snapshot (status timestamp 07:55, never updated since).

This PR only adds # comments — no docstring or mkdocs/nav changes — so there's nothing for griffe/fail_on_warning to trip on. Could you trigger a Read the Docs rebuild for this commit, or confirm the docs check isn't blocking the squash auto-merge? Thanks!