Fix non-deterministic issue ordering in SimpleMemory.record_issues

Preserve input order instead of converting from set, which caused
flaky test failures on Python 3.10.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: JihaoXin

ark/memory.py

@@ -268,7 +268,7 @@ def record_issues(self, issues: list, iteration: int):
                 # New issue — start at 1
                 self.issue_history[key] = 1
 
-        self.last_issues = list(current_keys)
+        self.last_issues = [self._issue_key(i) for i in issues]
         self.save()
 
     def get_repeat_issues(self, threshold: int = 3) -> List[Tuple[str, int]]: