fix: rename platform.py to vllm_platform.py to avoid stdlib shadowing

[dan-j-cooper]

platform.py shadows the stdlib module which causes a crash when running the server with uvicorn (which imports stdlib platform) added a prefix to resolve.

[Thump604]

Clean fix. Shadowing platform from stdlib is a real problem — uvicorn imports platform at the module level, and Python's import resolution picks up vllm_mlx/platform.py instead of the stdlib module when vllm-mlx is on the path. This causes a crash that's confusing to debug since the traceback points into uvicorn internals.

The rename covers all the right spots:

• vllm_mlx/__init__.py (lazy import)
• vllm_mlx/plugin.py (entry point string returned to vLLM)
• tests/test_platform.py (all 5 import sites)
• The pyproject.toml entry point goes through plugin.py:mlx_platform_plugin() which returns the string, so that's correctly handled indirectly.

One minor suggestion: you might consider keeping a thin platform.py shim that re-exports from vllm_platform.py with a deprecation warning, in case anyone has third-party code importing from vllm_mlx.platform import MLXPlatform directly. But given the project's stage, a clean break is probably fine.

+1 for merge.

[Thump604]

Straightforward fix. stdlib shadowing causes real crashes with uvicorn. +1

[waybarrios]

Reviewed the change. The rename covers all import sites correctly: init.py, plugin.py, tests, and the entry point string goes through plugin.py so pyproject.toml is handled indirectly. No missed references.