Blockquote autoformat must wrap nested quotes

Problem

The app's > autoformat rule still used the generic block autoformat path for blockquote.

That path assumes the target is a retaggable block. After blockquote became a container element, the rule still worked at the root through normalization, but it failed inside an existing quote where nested wrapping was required.

Symptoms

• In /blocks/editor-ai, typing > at the start of a paragraph inside a blockquote left > as plain text.
• Root-level > still produced a blockquote, so the regression only showed up once a quote already existed.
• A focused integration test reproduced the exact shape mismatch:
  • expected blockquote > blockquote > p
  • received blockquote > p with text > hello

What Didn't Work

• Treating this as another generic autoformat bug in packages/autoformat. The package-level block transform behaved exactly as designed for flat block types.
• Keeping the blockquote rule on type: KEYS.blockquote alone. That goes through setNodes, which is the wrong operation for a wrapper element.
• Using toggleBlock(..., { wrap: true }) for this seam. Inside an existing quote, toggle semantics can unwrap instead of nesting.

Solution

Make the app rule explicit about blockquote being a wrapper:

• set allowSameTypeAbove: true so the rule can fire while already inside a quote
• replace the generic retag behavior with editor.tf.wrapNodes({ type: KEYS.blockquote, children: [] })
• add an app integration test for both root > and nested > inside an existing quote

The fixed rule became:

{
  allowSameTypeAbove: true,
  format: (editor) => {
    editor.tf.wrapNodes({ children: [], type: KEYS.blockquote });
  },
  match: '> ',
  mode: 'block',
  type: KEYS.blockquote,
}

Why This Works

Nested quotes require one blockquote to wrap another block, not one block to change its type field.

wrapNodes(...) preserves that container relationship directly. allowSameTypeAbove: true removes the guard that previously blocked the rule the moment the cursor was already inside a quote.

Prevention

• When a node type becomes a wrapper/container, audit autoformat rules separately from toolbar and slash-command transforms.
• Generic block autoformat is safe for headings and paragraphs. It is not automatically safe for wrapper nodes like blockquote.
• If a rule should work both at the root and under the same ancestor type, review same-type guards before assuming the formatter is broken.
• Add one integration test for the root case and one nested case whenever autoformat behavior depends on container structure.

Related Issues

• #4898
• Related learning: 2026-04-02-blockquote-transforms-must-keep-selection-inside-the-new-quote