fix: do not lose paste data as code blocks

lib/src/plugins/markdown/decoder/parser/markdown_soft_code_block_parser.dart

@@ -0,0 +1,43 @@
+import 'package:appflowy_editor/appflowy_editor.dart';
+import 'package:markdown/markdown.dart' as md;
+
+/// Parses markdown code blocks (indentation or fenced) into paragraphs.
+/// This prevents code blocks from being dropped if the editor doesn't support them,
+/// and effectively strips indentation from 4-space indented blocks (as per md spec).
+class MarkdownSoftCodeBlockParser extends CustomMarkdownParser {
+  const MarkdownSoftCodeBlockParser();
+
+  @override
+  List<Node> transform(
+    md.Node node,
+    List<CustomMarkdownParser> parsers, {
+    MarkdownListType listType = MarkdownListType.unknown,
+    int? startNumber,
+  }) {
+    if (node is md.Element && node.tag == 'pre') {
+      String text = '';
+
+      if (node.children?.isNotEmpty == true) {
+        final codeNode = node.children!.first;
+        if (codeNode is md.Element && codeNode.tag == 'code') {
+          text = codeNode.textContent;
+        } else {
+          text = node.textContent;
+        }
+      } else {
+        text = node.textContent;
+      }
+
+      // Remove trailing newline which code blocks often have
+      if (text.endsWith('\n')) {
+        text = text.substring(0, text.length - 1);
+      }
+
+      // Split into multiple lines and create a paragraph for each
+      // This effectively "flattens" the code block into text
+      final lines = text.split('\n');
+      return lines.map((line) => paragraphNode(text: line)).toList();
+    }
+    return [];
+  }
+}

lib/src/plugins/markdown/decoder/parser/parser.dart

@@ -1,6 +1,7 @@
 export 'custom_markdown_node_parser.dart';
 export 'markdown_block_quote_parser.dart';
 export 'markdown_divider_parser.dart';
+export 'markdown_soft_code_block_parser.dart';
 export 'markdown_heading_parser.dart';
 export 'markdown_image_parser.dart';
 export 'markdown_ordered_list_item_parser.dart';

lib/src/plugins/markdown/document_markdown.dart

@@ -18,6 +18,7 @@ Document markdownToDocument(
     markdownParsers: [
       ...markdownParsers,
       const MarkdownParagraphParserV2(),
+      const MarkdownSoftCodeBlockParser(),
       const MarkdownHeadingParserV2(),
       const MarkdownTodoListParserV2(),
       const MarkdownUnorderedListParserV2(),