fix(editor): keep slash menu alive on text input when no_result (#14141)

**Problem**
Slash menu can be prematurely aborted when the query is still in
`no_result`
due to async query updates after deletion.

**Solution**
Keep the slash menu alive on text input while in `no_result`,
preventing aborts based on a stale query state.

**Repro**
1. Type `/eeee`
2. Delete to `/`
3. Type `h`
4. Slash menu should recover and show results


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

## Summary by CodeRabbit

* **Bug Fixes**
* Enhanced slash-menu keyboard interaction: users can now continue
typing to refine queries when no results are displayed, instead of the
menu closing unexpectedly. Keyboard navigation and other controls remain
responsive.

<sub>✏️ Tip: You can customize this high-level summary in your review
settings.</sub>

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

Co-authored-by: DarkSky <25152247+darkskygit@users.noreply.github.com>

blocksuite/affine/widgets/slash-menu/src/slash-menu-popover.ts

@@ -46,6 +46,22 @@ import {
   parseGroup,
   slashItemClassName,
 } from './utils.js';
+const isTextInputKey = (e: KeyboardEvent) => {
+  // Keys combined with modifiers are not considered text input
+  if (e.ctrlKey || e.metaKey || e.altKey) return false;
+
+  // During IME composition, do not treat keydown as text input.
+  // Query updates are handled by input/composition hooks.
+  if (e.isComposing) return false;
+
+  // Only allow single-character keys as text input
+  if (e.key.length !== 1) return false;
+
+  // Keep existing behavior: space closes the slash menu
+  if (e.key === ' ') return false;
+
+  return true;
+};
 type InnerSlashMenuContext = SlashMenuContext & {
   onClickItem: (item: SlashMenuActionItem) => void;
   searching: boolean;
@@ -228,10 +244,12 @@ export class SlashMenu extends WithDisposable(LitElement) {
         }
 
         if (key !== 'Backspace' && this._queryState === 'no_result') {
-          // if the following key is not the backspace key,
-          // the slash menu will be closed
-          this.abortController.abort();
-          return;
+          if (isTextInputKey(event)) {
+            // allow typing to change query; don't abort here
+          } else {
+            this.abortController.abort();
+            return;
+          }
         }
 
         if (key === 'Escape') {