fix: preserve node identity during type updates

[appflowy]

Summary

Small editor-only change to preserve node identity during safe block type conversions.

Scope is intentionally limited to appflowy-editor:

• Add UpdateNodeTypeOperation for same-node type/data updates.
• Add Transaction.updateNodeType and Document.updateNodeType.
• Allow Node.copyWith to preserve ids only when explicitly requested.
• Use in-place type updates for markdown shortcut conversions when descendant shape/content is unchanged.
• Emit and apply same-id type diffs from diffDocuments / EditorState.
• Resolve same-id type updates by stable node id when the operation path is stale.

Related GitHub Issues

• [Bug] created a page, now it won't open AppFlowy#8704 - document fails to open after toggle lists and images; reports Failed to apply update: block parent ... Type: 8.
• [Bug] msg: Failed to apply update: block parent <1360433027#10366> must be deleted or shared ref type. Type: 8 AppFlowy#8649 - same Type: 8 document-open failure on Linux.
• [Bug] only one particular page doesn't function AppFlowy#8427 - same failure around the 0.11.0 migration boundary.
• [Bug] Failed to apply update from persistent store: block parent <225509526#1786> must be deleted or shared ref type. Type: 8 AppFlowy#8124 - earlier multi-platform document corruption report repaired manually, without a code fix.
• [Bug] Grid Update Error AppFlowy#8414 - adjacent grid/database update error included in the investigation notes.

Why

The old markdown conversion path replaced a block with insert+delete even when only the block type changed. That regenerated node ids and made downstream clients treat a type conversion as a structural replacement. Desktop/web integration can use this operation to preserve block identity instead.

The user-reported historical context from AppFlowy PR #6516 was also checked before adding coverage. That earlier fix showed two important constraints:

• Conversions into childless block types, such as heading, must flatten nested children instead of keeping them inside the converted block.
• Undo/redo must be verified for both same-id conversions and flattening conversions.

Test Coverage

Core operation/document coverage:

• UpdateNodeTypeOperation serialization, inversion, copy, equality, and hash consistency.
• Document.updateNodeType / Transaction.updateNodeType preserve node id, children, external values, and metadata.
• diffDocuments emits UpdateNodeTypeOperation for same-id type changes.
• Remote/local apply handles UpdateNodeTypeOperation.
• Stale-path type updates resolve by nodeId instead of mutating the wrong path.
• Missing nodeId targets are skipped instead of applying to a stale path.
• Undo/redo for UpdateNodeTypeOperation preserves parent and child ids.

Markdown conversion coverage:

• Safe no-child conversion: paragraph -> heading preserves node id through undo/redo.
• Safe same-shape nested conversion: nested todo_list -> numbered_list preserves parent and child ids through undo/redo.
• Childless target conversion: nested numbered_list -> heading flattens children into siblings.
• Flattening undo/redo: undo restores the original nested numbered list, redo reapplies the heading plus flattened sibling list items.
• Existing nested bulleted_list -> heading flattening behavior remains covered.

Diff Size

• 13 files changed
• 606 insertions
• 13 deletions
• No desktop, Rust, web, vendored dependency, generated, or lockfile changes

Verification

• dart format --output=none --set-exit-if-changed ...
• git diff --check
• flutter test test/core/transform/operation_test.dart test/core/transform/transaction_test.dart test/new/block_component/heading_block_component/heading_character_shortcut_test.dart test/new/block_component/numbered_list_block_component/numbered_list_character_shortcut_test.dart

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✅ LucasXu0
❌ appflowy
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[appflowy]

Web AppFlowy-IO/AppFlowy-Web#325