feat: Add automatic perf runtime selection

[xieofxie]

Summary

• add auto as the default perf --runtime choice
• select winml-genai for model folders containing genai_config.json
• fall back to winml for all other model inputs while preserving explicit runtime choices
• cover automatic selection and CLI dispatch behavior with unit tests

[Qiong Wu (qiowu) (DingmaomaoBJTU)]

Auto runtime selection works for ordinary paths, but normalized local paths are not propagated to the GenAI dispatch path, causing valid bundle inputs such as ~/bundle to be misrouted after detection.

[Qiong Wu (qiowu) (DingmaomaoBJTU)]

Auto detection uses the normalized model path here, but _run_genai_runtime later reads the original value from ctx.params['model']. For example, normalize_model_arg expands ~/bundle, so this selects winml-genai, then the runner sees the unexpanded ~/bundle, Path(...).is_dir() is false, and it attempts to auto-build it as a model ID. Please pass the normalized model into the GenAI runner or synchronize ctx.params['model'] after normalization, and add a CLI-level regression test.