fix: enforce tool-based data only — Agent can no longer fabricate prices

- System prompt now has absolute rule: no tool result = no price
- Pre-market overview must call search_stock for each major stock
- Index futures explicitly marked as unsupported
- Training data prices explicitly declared outdated and forbidden
- Applied to both CN and EN prompts

agent/scheduler.go

@@ -24,6 +24,7 @@ func (s *Scheduler) Start(ctx context.Context) {
 		defer ticker.Stop()
 		lastReport := time.Time{}
 		lastCheck := time.Time{}
+		lastCleanup := time.Time{}
 
 		for {
 			select {
@@ -40,6 +41,13 @@ func (s *Scheduler) Start(ctx context.Context) {
 					s.riskCheck()
 					lastCheck = now
 				}
+				// Clean stale chat history every hour (sessions idle > 24h)
+				if now.Sub(lastCleanup) > 1*time.Hour {
+					if s.agent.history != nil {
+						s.agent.history.CleanOld(24 * time.Hour)
+					}
+					lastCleanup = now
+				}
 			}
 		}
 	}()