fix: pass MAX_MESSAGE_PAIRS_PER_AGENT to streaming conversation save (fixes #365)

The processStreamInBackground method was calling saveConversationExchange
without the maxHistorySize parameter, causing conversation history to grow
unbounded when using streaming responses regardless of MAX_MESSAGE_PAIRS_PER_AGENT
config. This aligns the streaming code path with the non-streaming path.

Author: octo-patch

typescript/src/orchestrator.ts

@@ -536,7 +536,8 @@ export class AgentSquad {
             this.storage,
             userId,
             sessionId,
-            agent.id
+            agent.id,
+            this.config.MAX_MESSAGE_PAIRS_PER_AGENT
           );
         }
       } else {