Function session_dir 

pub fn session_dir(data_dir: &Path, session_id: &str) -> PathBuf

The on-disk directory for one session’s event log and blobs, per spec §4.1: <data_dir>/<session_id>/.

data_dir ([session] data_dir, default .zeph/sessions) already names the sessions root — callers must not append an extra sessions segment (#5981).

Examples

use std::path::Path;

let dir = zeph_session::session_dir(Path::new(".zeph/sessions"), "abc-123");
assert_eq!(dir, Path::new(".zeph/sessions/abc-123"));