fix(editor): keyboard shortcuts in table cells (#15067)

## Description
Fixes keyboard shortcuts for text formatting (Ctrl+B, Ctrl+I, Ctrl+U,
etc.) not working inside table cells.
## Changes
- **Modified `table-cell.ts`**: Updated the `_handleKeyDown` method to
only prevent default behavior for Tab key and allow other keyboard
events to propagate, enabling text formatting shortcuts to work properly
- **Created `table-keymap.ts`**: New module that registers the
`textKeymap` for table blocks, ensuring text formatting shortcuts are
available in table cells
- **Updated `view.ts`**: Registered the `TableKeymapExtension` in the
table view extension setup
- **Cleaned up `format.ts`**: Removed unnecessary `TextSelection` check
that was preventing shortcuts from working in table contexts
## Closes
Closes #13916 #12127

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

* **Bug Fixes**
* Improved Tab key handling within table cells for more consistent
keyboard navigation.
* Simplified read-only detection for keyboard shortcuts to avoid
unexpected behavior.

* **Refactor**
* Reworked table keyboard mapping and registration to streamline
shortcut handling and event flow.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

blocksuite/affine/inlines/preset/src/keymap/format.ts

@@ -1,8 +1,4 @@
-import {
-  type BlockStdScope,
-  TextSelection,
-  type UIEventHandler,
-} from '@blocksuite/std';
+import { type BlockStdScope, type UIEventHandler } from '@blocksuite/std';
 
 import { textFormatConfigs } from '../command/index.js';
 
@@ -14,12 +10,9 @@ export const textFormatKeymap = (std: BlockStdScope) =>
         return {
           ...acc,
           [config.hotkey as string]: ctx => {
-            const { store: doc, selection } = std;
+            const { store: doc } = std;
             if (doc.readonly) return;
 
-            const textSelection = selection.find(TextSelection);
-            if (!textSelection) return;
-
             const allowed = config.textChecker?.(std.host) ?? true;
             if (!allowed) return;