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.

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.

Diff Size

• 10 files changed
• 299 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 origin/main...HEAD

Could not run targeted Flutter tests locally because this machine uses Flutter 3.27.4 while current main requires Flutter >=3.32.0 / .fvmrc specifies 3.38.5:

Because appflowy_editor requires Flutter SDK version >=3.32.0, version solving failed.

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[codecov]

Codecov Report

❌ Patch coverage is 90.17857% with 11 lines in your changes missing coverage. Please review.
✅ Project coverage is 72.44%. Comparing base (6fbe7ba) to head (94c2b97).

Files with missing lines	Patch %	Lines
lib/src/core/transform/operation.dart	85.41%	7 Missing ⚠️
lib/src/core/document/node.dart	50.00%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1202      +/-   ##
==========================================
+ Coverage   72.33%   72.44%   +0.11%     
==========================================
  Files         324      324              
  Lines       15900    16003     +103     
==========================================
+ Hits        11501    11594      +93     
- Misses       4399     4409      +10     

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