Function load_rules_from_directory 

pub fn load_rules_from_directory(
    dir: &Path,
    with_deprecated: bool,
) -> Result<Vec<Rule>>

Load all .RULE files from a directory into Rule values (backward-compatible).

This function loads rules and applies deprecated filtering during loading. For the two-stage pipeline, prefer load_loaded_rules_from_directory and build_index_from_loaded.

Kept for backward compatibility and testing despite not being used in production code. The new pipeline uses the two-stage loading process instead.