fix: preserve node identity during type updates

[appflowy]

Summary

Preserve editor node identity during safe block type conversions.

Changes:

• Add UpdateNodeTypeOperation for same-node type/data updates.
• Add Transaction.updateNodeType and Document.updateNodeType.
• Preserve ids through Node.copyWith when explicitly requested.
• Use in-place type updates for markdown shortcut conversions when descendant shape/content is unchanged.
• Emit same-id type diffs from diffDocuments and apply them in EditorState.

Why

The previous markdown conversion path replaced a block with insert+delete. That regenerated block ids and related child/text references even when only the block type changed. Desktop and web now rely on same-id type updates to avoid shared block reference corruption.

Verification

• dart format --output=none --set-exit-if-changed ...
• Attempted flutter test test/core/transform/operation_test.dart test/core/document/diff_test.dart test/core/document/node_test.dart, but this machine has Flutter 3.27.4 while this package requires Flutter >=3.32.0.

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