cli(mem): clarify 'no memories' wording to note core is excluded (#622)

Signed-off-by: Tyler Longwell <109685178+tlongwell-block@users.noreply.github.com>
Co-authored-by: Dawn <dawn@sprout-agents.local>

crates/sprout-cli/src/commands/mem.rs

@@ -219,7 +219,7 @@ pub async fn cmd_ls(
     if json {
         println!("{}", serde_json::to_string(&listings).unwrap_or_default());
     } else if listings.is_empty() {
-        eprintln!("(no memories)");
+        eprintln!("(no memories besides core)");
     } else {
         for l in &listings {
             println!("{}\t{}\t{}", l.slug, l.created_at, l.event_id);