fix(cron): preserve resolver call compatibility

Only fallback resolution needs an explicit target model. Keep the primary resolver call compatible with existing callers and test doubles while retaining atomic provider/model fallback selection.

cron/scheduler.py

@@ -3056,7 +3056,6 @@ def run_job(
             # example DeepSeek) for cron jobs that do not pin provider/model.
             runtime_kwargs = {
                 "requested": job.get("provider"),
-                "target_model": model or None,
             }
             if job.get("base_url"):
                 runtime_kwargs["explicit_base_url"] = job.get("base_url")