fix(system): sort recent tasks by finished_at desc

「最近任务」原先按 kv 键名排序；改为按 finished_at 倒序，
缺完成时间的排末尾。前端渲染侧同步按 finished_at 排序兜底。

reaction_board/web/queries.py

@@ -622,19 +622,32 @@ class DashboardQueries:
                 continue
         return None
 
+    @staticmethod
+    def _task_finished_sort_key(value: Any) -> tuple[int, int]:
+        """缺 finished_at 的排末尾；有值的按完成时间倒序。"""
+        if isinstance(value, Mapping):
+            raw = value.get("finished_at")
+            try:
+                return (0, -int(raw))
+            except (TypeError, ValueError):
+                pass
+        return (1, 0)
+
     def _task_records(self, conn: sqlite3.Connection) -> dict[str, Any]:
         rows = conn.execute(
-            "SELECT k, v FROM kv WHERE k LIKE 'task:last:%' ORDER BY k"
+            "SELECT k, v FROM kv WHERE k LIKE 'task:last:%'"
         ).fetchall()
-        result: dict[str, Any] = {}
+        items: list[tuple[str, Any]] = []
         for row in rows:
             name = str(row["k"]).removeprefix("task:last:")
             try:
                 value = json.loads(str(row["v"]))
             except (TypeError, json.JSONDecodeError):
                 value = {"raw": row["v"]}
-            result[name] = value
+            items.append((name, value))
-        return result
+        items.sort(key=lambda pair: self._task_finished_sort_key(pair[1]))
+        # 插入序即完成时间倒序；JSON/Object.entries 会保留。
+        return dict(items)
 
     def _task_running(self, conn: sqlite3.Connection) -> dict[str, Any]:
         rows = conn.execute(

reaction_board/web/static/views/system.js

@@ -6,7 +6,16 @@ import {
 } from "../format.js";
 
 function taskRows(tasks) {
-  const entries = Object.entries(tasks || {});
+  const entries = Object.entries(tasks || {}).sort((a, b) => {
+    const fa = Number(a[1] && a[1].finished_at);
+    const fb = Number(b[1] && b[1].finished_at);
+    const aOk = Number.isFinite(fa);
+    const bOk = Number.isFinite(fb);
+    if (aOk && bOk) return fb - fa;
+    if (aOk) return -1;
+    if (bOk) return 1;
+    return String(a[0]).localeCompare(String(b[0]));
+  });
   if (!entries.length) return emptyState("暂无任务记录", "运行一次同步、快照或发现后会写入最近结果。");
   return `<div class="table-wrap">
     <table class="data-table">

tests/test_web_queries.py

@@ -681,6 +681,48 @@ def test_overview_adjacent_previous_with_seed_and_dual_fields():
         finally:
             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。"""
+    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
+            samples = (
+                ("zzz_old", FIXED_NOW - 300),
+                ("aaa_mid", FIXED_NOW - 100),
+                ("mmm_new", FIXED_NOW - 10),
+                ("no_time", None),
+            )
+            for name, finished in samples:
+                payload = {
+                    "name": name,
+                    "ok": True,
+                    "started_at": (finished - 5) if finished is not None else FIXED_NOW,
+                    "error": None,
+                    "summary": {},
+                }
+                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()
+            system = q.system()
+            assert list(system["tasks"].keys()) == [
+                "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()
+
+
 def main_test():
     test_overview()
     test_video_listing_filters_and_sorting()
@@ -696,6 +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_growth_auto_falls_back_to_one_day()
     test_snapshot_recent_next_run_follows_completion()
     test_overview_adjacent_previous_with_seed_and_dual_fields()