refactor(goals): share one dropped-write warning across managers

Review fixups for #88965. The goal, loop, and heartbeat managers each
had a copy of the same WARNING text. The shared _warn_dropped_write
helper in goals.py keeps the three logs identical and greppable as one
bug class. The _warm_goals_session_db parameter is now label. The old
name ctx said context, but the value is a log label.

hermes_cli/heartbeat.py

@@ -184,12 +184,9 @@ def save_heartbeat(session_id: str, state: HeartbeatState) -> None:
         return
     db = _get_session_db()
     if db is None:
-        logger.warning(
-            "HeartbeatManager: heartbeat for %s not persisted — session "
-            "DB unavailable (bootstrap window exceeded, in-memory state "
-            "still active)",
-            session_id,
-        )
+        from hermes_cli.goals import _warn_dropped_write
+
+        _warn_dropped_write("HeartbeatManager", "heartbeat", session_id)
         return
     try:
         db.set_meta(_meta_key(session_id), state.to_json())