baseline: setup failure is not recorded as a result; repair_stats tolerates a missing trajectory

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_014aUaQeLnwbb1zTpN7kHeat

harness/runner.py

@@ -96,6 +96,8 @@ def repair_stats(path):
     import hashlib
     last = None  # (object, md5, failed)
     after = changed = 0
+    if not os.path.exists(path):  # setup failed: no agent run, no trajectory
+        return {"pushes_after_error": None, "pushes_changed_after_error": None, "repair_rate": None}
     for line in open(path):
         e = json.loads(line)
         if e.get("tool") != "sap_push_source" or (e["result"].startswith("Tool ") and e["is_error"]):