fix: ai button should not display in readonly mode (#7415)

[BS-737](https://linear.app/affine-design/issue/BS-737/shared-page-也可以用-ai)

packages/frontend/core/src/blocksuite/presets/ai/entries/code-toolbar/setup-code-toolbar.ts

@@ -33,7 +33,7 @@ export function setupCodeToolbarEntry(codeToolbar: AffineCodeToolbarWidget) {
         name: 'Ask AI',
         tooltip: 'Ask AI',
         icon: AIStarIcon,
-        showWhen: () => true,
+        showWhen: CodeBlockComponent => !CodeBlockComponent.doc.readonly,
         render(codeBlock: CodeBlockComponent, onClick?: () => void) {
           return html`<ask-ai-button
             class="code-toolbar-button ask-ai"

packages/frontend/core/src/blocksuite/presets/ai/entries/image-toolbar/setup-image-toolbar.ts

@@ -44,7 +44,7 @@ export function setupImageToolbarEntry(imageToolbar: AffineImageToolbarWidget) {
             }}
           ></ask-ai-button>`;
         },
-        showWhen: () => true,
+        showWhen: imageBlockComponent => !imageBlockComponent.doc.readonly,
       },
     ],
     0