Function init_tracing_from_config 

pub fn init_tracing_from_config(
    config: &ObservabilityConfig,
) -> Result<(), TryInitError>

Initialize structured logging from an ObservabilityConfig.

Respects RUST_LOG env var if set; otherwise uses config.log_level. When log_format is "json", emits machine-readable JSON lines. When audit_log_path is set, appends an additional JSON log file at INFO level for audit trail purposes.

Errors

Returns TryInitError if a global tracing subscriber has already been installed (e.g. by a previous call to this function or init_tracing). Callers that want to tolerate double-initialization (such as test harnesses) can ignore the error.