Function dispatch_event 

pub fn dispatch_event(
    conn: &Connection,
    event: &str,
    memory_id: &str,
    namespace: &str,
    agent_id: Option<&str>,
    db_path: &Path,
)

Fire an event to all matching subscribers. Each dispatch runs in its own OS thread and does NOT block the caller. Errors are logged and counted in the DB via failure_count.

Caller owns the connection. Dispatch threads re-open the connection as needed to update counters (cheap — SQLite connections are process-shared via WAL).