Function load_config 

pub fn load_config() -> Result<(Config, Option<UnifiedConfig>, Vec<String>), ConfigLoadWithValidationError>

Load configuration with the unified approach.

This function loads configuration from the unified config file (~/.config/ralph-workflow.toml) and applies environment variable overrides.

Returns

Returns a tuple of (Config, Vec<String>) where the second element contains any deprecation warnings to be displayed to the user.

Errors

Returns error if the operation fails.