fix(patch): cherry-pick ee6556c to release/v0.21.0-preview.1-pr-14691 to patch version v0.21.0-preview.1 and create version 0.21.0-preview.2 (#14908)

Co-authored-by: Jack Wotherspoon <jackwoth@google.com>

packages/cli/src/ui/AppContainer.tsx

@@ -63,7 +63,7 @@ import {
   SessionEndReason,
   fireSessionStartHook,
   fireSessionEndHook,
-  generateAndSaveSummary,
+  generateSummary,
 } from '@google/gemini-cli-core';
 import { validateAuthMethod } from '../config/auth.js';
 import process from 'node:process';
@@ -312,9 +312,13 @@ export const AppContainer = (props: AppContainerProps) => {
           : SessionStartSource.Startup;
         await fireSessionStartHook(hookMessageBus, sessionStartSource);
       }
+
+      // Fire-and-forget: generate summary for previous session in background
+      generateSummary(config).catch((e) => {
+        debugLogger.warn('Background summary generation failed:', e);
+      });
     })();
     registerCleanup(async () => {
-      await generateAndSaveSummary(config);
       // Turn off mouse scroll.
       disableMouseEvents();
       const ideClient = await IdeClient.getInstance();