fix(cli): write JSON output to stdout instead of stderr

Fixes bounty issue #1495

When using --json or --jsonl output format, JSON event objects were being
written to stderr (eprintln!) instead of stdout (println!). This caused
malformed output when piping to tools like jq, as the JSON events would
appear in the terminal while the final result was piped to the destination.

Changed eprintln! to println! for JSON event output and error JSON output
to ensure all JSON data goes to stdout for proper piping support.

Author: factorydroid

cortex-cli/src/run_cmd.rs

@@ -554,10 +554,10 @@ impl RunCli {
 
                 match self.format {
                     OutputFormat::Json => {
-                        eprintln!("{}", serde_json::to_string(&event_json)?);
+                        println!("{}", serde_json::to_string(&event_json)?);
                     }
                     OutputFormat::Jsonl => {
-                        eprintln!("{}", serde_json::to_string(&event_json)?);
+                        println!("{}", serde_json::to_string(&event_json)?);
                     }
                     _ => {}
                 }
@@ -636,7 +636,7 @@ impl RunCli {
                             "message": e.message,
                             "session_id": session_id,
                         });
-                        eprintln!("{}", serde_json::to_string(&err_json)?);
+                        println!("{}", serde_json::to_string(&err_json)?);
                     } else {
                         eprintln!(
                             "{}Error:{} {}",