Function init 

pub fn init() -> SafLogLayer

Initialize the SAF log layer from environment variables.

Reads:

• SAF_LOG: filter specification (if absent, returns a no-op layer)
• SAF_LOG_FILE: output file path (if absent, writes to stderr)

Returns a SafLogLayer to compose into a tracing subscriber:

use tracing_subscriber::prelude::*;
let saf_layer = saf_core::logging::subscriber::init();
tracing_subscriber::registry()
    .with(tracing_subscriber::fmt::layer())
    .with(saf_layer)
    .init();

Panics

Panics if SAF_LOG_FILE is set but the file cannot be created.