fix(system): sort recent tasks by started_at desc

进行中任务可能尚无 finished_at；改为按 started_at 倒序，
缺开始时间的排末尾。测例用 finished 错开，避免误用完成时间。

tests/test_web_queries.py

@@ -682,33 +682,34 @@ def test_overview_adjacent_previous_with_seed_and_dual_fields():
             db.close()
 
 
-def test_system_tasks_sorted_by_finished_at_desc():
-    """最近任务按 finished_at 倒序；缺时间的排末尾。"""
+def test_system_tasks_sorted_by_started_at_desc():
+    """最近任务按 started_at 倒序；缺开始时间的排末尾（含进行中无 finished）。"""
     import json
 
     with tempfile.TemporaryDirectory() as tmp:
         db, q = setup(tmp)
         try:
             repo = Repository(db)
-            # 故意打乱写入/键名字母序，避免 ORDER BY k 碰巧正确
+            # 故意打乱写入/键名字母序；finished_at 与 started_at 错开，避免误用完成时间
             samples = (
-                ("zzz_old", FIXED_NOW - 300),
-                ("aaa_mid", FIXED_NOW - 100),
-                ("mmm_new", FIXED_NOW - 10),
-                ("no_time", None),
+                # name, started_at, finished_at
+                ("zzz_old", FIXED_NOW - 300, FIXED_NOW - 10),   # 开始最早，完成却很晚
+                ("aaa_mid", FIXED_NOW - 100, FIXED_NOW - 90),
+                ("mmm_new", FIXED_NOW - 10, None),              # 进行中：只有 started
+                ("no_time", None, FIXED_NOW),                  # 缺 started，应末尾
             )
-            for name, finished in samples:
+            for name, started, finished in samples:
                 payload = {
                     "name": name,
-                    "ok": True,
-                    "started_at": (finished - 5) if finished is not None else FIXED_NOW,
+                    "ok": True if finished is not None else True,
                     "error": None,
                     "summary": {},
                 }
+                if started is not None:
+                    payload["started_at"] = started
                 if finished is not None:
                     payload["finished_at"] = finished
                 repo.kv_set(f"task:last:{name}", json.dumps(payload))
-            # 清掉 fixture 里的旧任务，只保留本用例
             for legacy in ("snapshot", "fans", "discovery"):
                 repo.kv_delete(f"task:last:{legacy}")
             DASHBOARD_CACHE.clear()
@@ -717,7 +718,6 @@ def test_system_tasks_sorted_by_finished_at_desc():
                 "mmm_new", "aaa_mid", "zzz_old", "no_time",
             ]
             overview = q.overview()
-            # overview 也走 _task_records，顺序应一致
             assert list(overview["tasks"].keys()) == list(system["tasks"].keys())
         finally:
             db.close()
@@ -738,7 +738,7 @@ def main_test():
     test_fans_candidates_system_and_export()
     test_system_status_uses_completed_date_and_running_flags()
     test_system_next_runs_follow_last_completion_not_wall_clock()
-    test_system_tasks_sorted_by_finished_at_desc()
+    test_system_tasks_sorted_by_started_at_desc()
     test_growth_auto_falls_back_to_one_day()
     test_snapshot_recent_next_run_follows_completion()
     test_overview_adjacent_previous_with_seed_and_dual_fields()