feat(editor): support markdown adapter preprocessed with latex delimiters (#11431)

To close [BS-2870](https://linear.app/affine-design/issue/BS-2870/支持识别-和-[-包裹内容为公式)

## Add Markdown Preprocessor Extension and Enhanced LaTeX Support

### Markdown Preprocessor Extension
This PR introduces a new preprocessor extension for Markdown adapters that allows preprocessing of content before conversion:

Adds a new PreprocessorManager for handling text transformations
Introduces extensible preprocessor interface that supports different processing levels (block/slice/doc)

Integrates preprocessor extension into the existing Markdown adapter workflow

### LaTeX Support Enhancement
Extends LaTeX support to handle both traditional and alternative syntax:
Adds support for backslash LaTeX syntax:

Block math: ```\[...\] ``` alongside existing ```$$...$$```
Inline math: ```\(...\) ``` alongside existing ```$...$```

Implements LaTeX preprocessor to standardize syntax before conversion

Updates tests to cover both syntax variants

blocksuite/affine/blocks/block-code/src/adapters/extension.ts

@@ -1,13 +1,13 @@
 import type { ExtensionType } from '@blocksuite/store';
 
 import { CodeBlockHtmlAdapterExtension } from './html.js';
-import { CodeBlockMarkdownAdapterExtension } from './markdown.js';
+import { CodeBlockMarkdownAdapterExtensions } from './markdown/index.js';
 import { CodeBlockNotionHtmlAdapterExtension } from './notion-html.js';
 import { CodeBlockPlainTextAdapterExtension } from './plain-text.js';
 
 export const CodeBlockAdapterExtensions: ExtensionType[] = [
   CodeBlockHtmlAdapterExtension,
-  CodeBlockMarkdownAdapterExtension,
+  CodeBlockMarkdownAdapterExtensions,
   CodeBlockPlainTextAdapterExtension,
   CodeBlockNotionHtmlAdapterExtension,
-];
+].flat();

blocksuite/affine/blocks/block-code/src/adapters/index.ts

@@ -1,4 +1,4 @@
 export * from './html.js';
-export * from './markdown.js';
+export * from './markdown/index.js';
 export * from './notion-html.js';
 export * from './plain-text.js';

blocksuite/affine/blocks/block-code/src/adapters/markdown/index.ts

@@ -0,0 +1,12 @@
+import type { ExtensionType } from '@blocksuite/store';
+
+import { CodeBlockMarkdownAdapterExtension } from './markdown.js';
+import { CodeMarkdownPreprocessorExtension } from './preprocessor.js';
+
+export * from './markdown.js';
+export * from './preprocessor.js';
+
+export const CodeBlockMarkdownAdapterExtensions: ExtensionType[] = [
+  CodeMarkdownPreprocessorExtension,
+  CodeBlockMarkdownAdapterExtension,
+];

blocksuite/affine/blocks/block-code/src/adapters/markdown/preprocessor.ts

@@ -0,0 +1,76 @@
+import {
+  type MarkdownAdapterPreprocessor,
+  MarkdownPreprocessorExtension,
+} from '@blocksuite/affine-shared/adapters';
+
+const codePreprocessor: MarkdownAdapterPreprocessor = {
+  name: 'code',
+  levels: ['slice'],
+  preprocess: content => {
+    let codeFence = '';
+    const lines = content
+      .split('\n')
+      .map(line => {
+        if (line.trimStart().startsWith('-')) {
+          return line;
+        }
+        let trimmedLine = line.trimStart();
+        if (!codeFence && trimmedLine.startsWith('```')) {
+          codeFence = trimmedLine.substring(
+            0,
+            trimmedLine.lastIndexOf('```') + 3
+          );
+          if (codeFence.split('').every(c => c === '`')) {
+            return line;
+          }
+          codeFence = '';
+        }
+        if (!codeFence && trimmedLine.startsWith('~~~')) {
+          codeFence = trimmedLine.substring(
+            0,
+            trimmedLine.lastIndexOf('~~~') + 3
+          );
+          if (codeFence.split('').every(c => c === '~')) {
+            return line;
+          }
+          codeFence = '';
+        }
+        if (
+          !!codeFence &&
+          trimmedLine.startsWith(codeFence) &&
+          trimmedLine.lastIndexOf(codeFence) === 0
+        ) {
+          codeFence = '';
+        }
+        if (codeFence) {
+          return line;
+        }
+
+        trimmedLine = trimmedLine.trimEnd();
+        if (!trimmedLine.startsWith('<') && !trimmedLine.endsWith('>')) {
+          // check if it is a url link and wrap it with the angle brackets
+          // sometimes the url includes emphasis `_` that will break URL parsing
+          //
+          // eg. /MuawcBMT1Mzvoar09-_66?mode=page&blockIds=rL2_GXbtLU2SsJVfCSmh_
+          // https://www.markdownguide.org/basic-syntax/#urls-and-email-addresses
+          try {
+            const valid =
+              URL.canParse?.(trimmedLine) ?? Boolean(new URL(trimmedLine));
+            if (valid) {
+              return `<${trimmedLine}>`;
+            }
+          } catch (err) {
+            console.log(err);
+          }
+        }
+
+        return line.replace(/^ /, '&#x20;');
+      })
+      .join('\n');
+
+    return lines;
+  },
+};
+
+export const CodeMarkdownPreprocessorExtension =
+  MarkdownPreprocessorExtension(codePreprocessor);