perf: 优化 Agent 流式会话处理

- 合并流式通知与持久化写入，限制浏览器会话缓存

- 增量投影轮次事件并稳定关联异步工具任务

easyflow-ui-admin/app/src/views/ai/agents/composables/useAgentTryoutStream.ts

@@ -114,6 +114,7 @@ export function useAgentTryoutStream() {
     const sessionChanged = activeSessionId !== sessionId;
     activeSessionId = sessionId;
     if (!rawRounds || sessionChanged) {
+      rawRounds?.flush();
       rawRounds = useAgentTryoutRawRounds({
         mode: 'draft',
         sessionId,
@@ -174,12 +175,18 @@ export function useAgentTryoutStream() {
     const payload = envelope.payload || {};
 
     if (activeRoundId) {
-      rawRounds?.recordEvent(activeRoundId, {
+      const runtimeEvent = rawRounds?.recordEvent(activeRoundId, {
         domain,
         payload,
         type,
       });
-      rebuildTimeline();
+      if (runtimeEvent) {
+        rawRounds?.projectEvent(
+          timelineItems.value,
+          activeRoundId,
+          runtimeEvent,
+        );
+      }
     }
 
     if (domain === 'LLM' && type === 'MESSAGE') {
@@ -340,12 +347,23 @@ export function useAgentTryoutStream() {
     finishStoppedRun();
   }
 
+  function dispose() {
+    if (loading.value) {
+      userStopped = true;
+      sseClient.abort();
+      finishStoppedRun();
+      return;
+    }
+    rawRounds?.flush();
+  }
+
   return {
     loading,
     clearDraftSession,
     markToolApproving,
     markToolRejected,
     copyMessageText,
+    dispose,
     regenerateDraft,
     selectVariant,
     syncDraftContext,