fix: chat block peek view input reset height (#7884)

[BS-1202](https://linear.app/affine-design/issue/BS-1202/ai-chat-block-输入大段内容发送后输入框-resize-问题)

packages/frontend/core/src/blocksuite/presets/ai/peek-view/chat-block-input.ts

@@ -362,6 +362,7 @@ export class ChatBlockInput extends LitElement {
     const { doc } = this.host;
     this.textarea.value = '';
     this._isInputEmpty = true;
+    this.textarea.style.height = 'unset';
     this.updateContext({
       images: [],
       status: 'loading',