feat(hub): background chart poll with SSE for positions and market watch

Co-authored-by: Cursor <cursoragent@cursor.com>

hub_kline_store.py

@@ -286,10 +286,11 @@ def resolve_chart_bars(
     *,
     db_path: Path | None = None,
     force_refresh: bool = False,
+    tail_refresh: bool = False,
 ) -> dict[str, Any]:
     """
     按需：先读库，不足则 remote_fetch(symbol, timeframe, since_ms, limit) 补齐并写库。
-    无后台定时任务；每次调用时顺带 purge 15 天前数据。
+    tail_refresh=True 时即使库内「够新」也增量拉取尾部 K 线（未收盘 K 的 OHLC 更新）。
     """
     init_db(db_path)
     purged = purge_retention(db_path)
@@ -317,6 +318,10 @@ def resolve_chart_bars(
     period_ms = TIMEFRAME_MS[tf]
     newest_ok = newest_db is not None and int(newest_db) >= int(last_closed) - period_ms
     need_fetch = force_refresh or len(db_rows) < need or not newest_ok
+    tail_only = False
+    if tail_refresh and db_rows and not force_refresh and not need_fetch:
+        need_fetch = True
+        tail_only = True
 
     fetched = 0
     price_tick: Optional[float] = None
@@ -324,8 +329,10 @@ def resolve_chart_bars(
 
     if need_fetch:
         since = fetch_start_ms
+        if tail_only and newest_db is not None:
+            since = max(0, int(newest_db) - period_ms * 3)
         # 仅当库内根数已够且缺口在尾部时做增量拉取；否则全量回看，避免 Gate from>to
-        if (
+        elif (
             db_rows
             and not force_refresh
             and newest_ok