fix(harness): replace implicit .harness-active absence with explicit .harness-reflect marker for self-reflect triggering

Fixes two bugs:
- False positive: stale harness-tasks.json from previous runs triggered self-reflect when harness wasn't active
- False negative: self-reflect didn't trigger after harness completed all tasks

Generated with SWE-Agent.ai

Co-Authored-By: SWE-Agent.ai <noreply@swe-agent.ai>

skills/harness/hooks/harness-stop.py

@@ -260,6 +260,11 @@ def main() -> int:
     # If nothing left to do, allow stop
     if not pending_eligible and not retryable and not in_progress_blocking:
         _reset_block_counter(root)
+        # Signal self-reflect hook BEFORE removing active marker
+        try:
+            (root / ".harness-reflect").touch()
+        except Exception:
+            pass
         try:
             (root / ".harness-active").unlink(missing_ok=True)
         except Exception: