feat(core): render session title in ai session history (#13147)

Close [AI-331](https://linear.app/affine-design/issue/AI-331)

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

* **Improvements**
* Session history now displays the session title (or "New chat" if
unavailable) instead of the session ID for a clearer user experience.

* **Performance**
* Recent copilot chat session lists now load faster by excluding message
details from the initial query.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

packages/frontend/core/src/blocksuite/ai/components/ai-chat-toolbar/ai-session-history.ts

@@ -225,7 +225,7 @@ export class AISessionHistory extends WithDisposable(ShadowlessElement) {
               }}
             >
               <div class="ai-session-title">
-                ${session.sessionId}
+                ${session.title || 'New chat'}
                 <affine-tooltip .offsetX=${60}>
                   Click to open this chat
                 </affine-tooltip>