API: preprocessing.cleaning

skyulf.preprocessing.cleaning

Cleaning nodes (Text / InvalidValue / ValueReplacement / AliasReplacement).

Each Applier dispatches on engine via apply_dual_engine so per-engine logic lives in small _apply_polars / _apply_pandas static helpers. Per-operation work is further split into module-level helpers (_trim_*, _case_*, _remove_special_*, _regex_*, _invalid_rule_*) plus small dispatch dicts so individual methods stay at CCN ≤ 8.