fix: harden ghost client cleanup and PRE_ACTIVE state guard

- Change ChannelState.PRE_ACTIVE from list to frozenset (immutable,
  O(1) membership tests, no risk of silent mutation)

- Add optional client_ids parameter to ClientManager.remove_ghost_clients()
  so callers that have already fetched SMEMBERS can pass it through,
  eliminating a redundant Redis round-trip

- Pass pre-fetched client_ids from get_basic_channel_info() into
  remove_ghost_clients() to remove the duplicate SMEMBERS call

apps/proxy/ts_proxy/channel_status.py

@@ -445,8 +445,9 @@ class ChannelStatus:
             client_ids = proxy_server.redis_client.smembers(client_set_key)
 
             # Remove ghost SET entries before building the client list.
+            # Pass the already-fetched client_ids to avoid a redundant SMEMBERS.
             stale_client_ids = ClientManager.remove_ghost_clients(
-                proxy_server.redis_client, channel_id
+                proxy_server.redis_client, channel_id, client_ids=client_ids
             )
             if stale_client_ids:
                 client_count = max(0, client_count - len(stale_client_ids))

apps/proxy/ts_proxy/client_manager.py

@@ -415,14 +415,20 @@ class ClientManager:
             logger.error(f"Error refreshing client TTL: {e}")
 
     @staticmethod
-    def remove_ghost_clients(redis_client, channel_id):
+    def remove_ghost_clients(redis_client, channel_id, client_ids=None):
         """Remove client SET entries whose metadata hash has expired.
 
         Returns the list of removed (stale) client IDs, or an empty list
         if none were found. Uses a pipelined EXISTS check for efficiency.
+
+        Args:
+            client_ids: Optional pre-fetched result of SMEMBERS for this
+                        channel. Pass this to avoid a redundant SMEMBERS
+                        call when the caller has already fetched it.
         """
         client_set_key = RedisKeys.clients(channel_id)
-        client_ids = redis_client.smembers(client_set_key)
+        if client_ids is None:
+            client_ids = redis_client.smembers(client_set_key)
         if not client_ids:
             return []
 

apps/proxy/ts_proxy/constants.py

@@ -22,7 +22,7 @@ class ChannelState:
 
     # States before a channel is fully active. Used by the stream manager
     # finally block to decide whether a failed stream can write ERROR.
-    PRE_ACTIVE = [INITIALIZING, CONNECTING, BUFFERING, WAITING_FOR_CLIENTS]
+    PRE_ACTIVE = frozenset([INITIALIZING, CONNECTING, BUFFERING, WAITING_FOR_CLIENTS])
 
 # Event types
 class EventType: