fix(core): editor blur unexpectedly when clicking blank area (#10501)

### Before

https://github.com/user-attachments/assets/3c4b20e1-6d89-4dc7-a51f-04b6e9a89486

### After

https://github.com/user-attachments/assets/86b93403-597e-4dbb-ab65-90908342c230

blocksuite/affine/block-note/src/commands/focus-block-end.ts

@@ -4,14 +4,23 @@ import {
   TextSelection,
 } from '@blocksuite/block-std';
 
+/**
+ * Focus the end of the block
+ * @param focusBlock - The block to focus
+ * @param force - If set to true, the selection will be cleared.
+ * It is useful when the selection is same.
+ */
 export const focusBlockEnd: Command<{
   focusBlock?: BlockComponent;
+  force?: boolean;
 }> = (ctx, next) => {
-  const { focusBlock, std } = ctx;
+  const { focusBlock, force, std } = ctx;
   if (!focusBlock || !focusBlock.model.text) return;
 
   const { selection } = std;
 
+  if (force) selection.clear();
+
   selection.setGroup('note', [
     selection.create(TextSelection, {
       from: {

packages/frontend/core/src/blocksuite/block-suite-editor/blocksuite-editor-container.tsx

@@ -151,6 +151,7 @@ export const BlocksuiteEditorContainer = forwardRef<
         const focusBlock = std.view.getBlock(lastBlock.id) ?? undefined;
         std.command.exec(focusBlockEnd, {
           focusBlock,
+          force: true,
         });
         return;
       }

tests/affine-local/e2e/blocksuite/editor.spec.ts

@@ -1,4 +1,5 @@
 import { test } from '@affine-test/kit/playwright';
+import { locateEditorContainer } from '@affine-test/kit/utils/editor';
 import { openHomePage } from '@affine-test/kit/utils/load-page';
 import {
   addDatabase,
@@ -82,7 +83,15 @@ test('append paragraph when click editor gap', async ({ page }) => {
   await page.locator('[data-testid=page-editor-blank]').click();
   expect(await paragraph.count()).toBe(numParagraphs + 1);
 
-  // click the gap again, should not append another paragraph
   await page.locator('[data-testid=page-editor-blank]').click();
-  expect(await paragraph.count()).toBe(numParagraphs + 1);
+  expect(
+    await paragraph.count(),
+    'click the gap again, should not append another paragraph'
+  ).toBe(numParagraphs + 1);
+
+  const editorContainer = locateEditorContainer(page);
+  expect(
+    await editorContainer.evaluate(el => el.contains(document.activeElement)),
+    'editor should should keep being focused'
+  ).toBe(true);
 });