mirror claude stderr to tracing so journald captures it

bus-only note made post-mortems require the web UI / events sqlite;
now stderr lines also land in 'journalctl -M <container> -b' alongside
the existing LiveEvent::Note for the dashboard.

hive-ag3nt/src/turn.rs

@@ -290,6 +290,11 @@ async fn run_claude(prompt: &str, files: &TurnFiles, bus: &Bus) -> Result<bool>
             if line.contains(PROMPT_TOO_LONG_MARKER) {
                 flag_err.store(true, Ordering::Relaxed);
             }
+            // Mirror to journald so post-mortems work without the web UI
+            // or the events sqlite. The bus event is what the dashboard
+            // renders; the tracing line is what `journalctl -M <c> -b`
+            // surfaces when claude exits non-zero.
+            tracing::warn!(line = %line, "claude stderr");
             bus_err.emit(LiveEvent::Note(format!("stderr: {line}")));
         }
     });