Stream real-time position quotes via tick-driven SSE with incremental UI updates.

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

position_stream.py

@@ -50,8 +50,7 @@ class PositionStreamHub:
             self._snapshot = dict(data)
             self._snapshot_ts = time.time()
 
-    def broadcast(self, event: str, data: dict) -> None:
-        self.set_snapshot(data)
+    def _fanout(self, event: str, data: dict) -> None:
         msg = {"event": event, "data": data}
         with self._lock:
             subs = list(self._subs)
@@ -68,6 +67,14 @@ class PositionStreamHub:
                 except queue.Full:
                     pass
 
+    def broadcast(self, event: str, data: dict) -> None:
+        self.set_snapshot(data)
+        self._fanout(event, data)
+
+    def push_event(self, event: str, data: dict) -> None:
+        """SSE 推送，不覆盖 positions 全量快照。"""
+        self._fanout(event, data)
+
 
 position_hub = PositionStreamHub()