fix(quickadapter): support CatBoost continual learning (#196)

fix(quickadapter): support CatBoost continual learning (#196)

* fix(quickadapter): support CatBoost continual learning

* fix(quickadapter): drop CatBoost init_model on GPU task_type

CatBoost init_model training continuation is CPU-only and raises
"Training continuation for GPU is not yet supported" on GPU. Passing it
unconditionally crashed GPU CatBoost retrains under continual_learning.
Drop init_model on the GPU path so it cold-starts instead.

* style(quickadapter): realign README table cells after continual-learning doc edits