feat: harden support, localize knowledge and add operator availability [skip ci]

Source-only publication of reviewed commit 64e96a7f423673dc29ad56485be9fc79bce8af1c.

Passed in isolation: focused frontend/backend tests, race checks, TypeScript typecheck, lint, Go compilation, Flowgram build, and deterministic SDK build/tests.

Not accepted as a production release: Next.js export/native assembly remains blocked by environment memory limits; browser interaction and MySQL staging acceptance remain unverified. No production server, database/schema, runtime configuration, deployment, release tag, or workflow execution was performed.

Expected source tree: 0a4a7528e9.

internal/services/ws_connection_manager.go

@@ -1,3 +1,5 @@
+// Modified in the independent hardening fork; see docs/hardening.
+
 package services
 
 import "sync"
@@ -23,6 +25,9 @@ func (m *WsConnectionManager) Register(session *ClientSession, defaultTopics []s
 	m.mu.Lock()
 	defer m.mu.Unlock()
 
+	if session.Closed.Load() {
+		return len(m.sessions)
+	}
 	m.sessions[session.ID] = session
 	for _, topic := range defaultTopics {
 		m.subscribeLocked(session, topic)
@@ -53,6 +58,9 @@ func (m *WsConnectionManager) Subscribe(session *ClientSession, topics []string)
 	m.mu.Lock()
 	defer m.mu.Unlock()
 
+	if session.Closed.Load() {
+		return nil
+	}
 	ret := make([]string, 0, len(topics))
 	for _, topic := range topics {
 		if _, exists := session.Topics[topic]; exists {
@@ -132,3 +140,16 @@ func (m *WsConnectionManager) unsubscribeLocked(session *ClientSession, topic st
 	}
 	delete(session.Topics, topic)
 }
+
+func (m *WsConnectionManager) TopicList(session *ClientSession) []string {
+	m.mu.RLock()
+	defer m.mu.RUnlock()
+	if session == nil {
+		return nil
+	}
+	topics := make([]string, 0, len(session.Topics))
+	for topic := range session.Topics {
+		topics = append(topics, topic)
+	}
+	return topics
+}