Fix sweep match metadata parsing

[devshahofficial]

Summary

• Treat self-play match sweep settings as sweep metadata instead of hyperparameter definitions.
• Add a config regression covering the default + breakout sweep config path.

Root cause

The match sweep keys added under [sweep] are scalar settings. _params_from_puffer_sweep expected every non-metadata key in that section to be a hyperparameter dict, so puffer sweep breakout raised AssertionError: Param match_enemy_model_path is not a dict.

Validation

• python -m pytest tests/test_sweep_config.py tests/test_import_performance.py -q
• Direct parse of config/default.ini + config/breakout.ini through _params_from_puffer_sweep

Fixes #589