Markdown ordered list restarts must emit listRestartPolite

Problem

deserializeMd(...) already read ordered-list starts correctly from markdown. A list like:

2. Second list item
3. Third list item

produced nodes with listStart: 2 and listStart: 3.

The bug showed up one step later. Once that value went through editor.tf.setValue(...), the first item lost listStart, and the following item got renumbered from the wrong base.

Root cause

The list plugin normalizer does not treat listStart alone as authoritative for the first item in a list.

For a first list item with a number above 1, it expects restart metadata:

• listRestart
• or listRestartPolite

Without one of those fields, normalization assumes the list should start at 1, strips the first item's listStart, and recomputes later siblings from there.

The markdown deserializer emitted listStart, but it did not emit the restart metadata that the list normalizer relies on.

Fix

When deserializing the first node of an ordered list whose markdown start is above 1, emit listRestartPolite alongside listStart:

if (isOrdered) {
  itemContent.listStart = startIndex + index;

  if (index === 0 && nodeIndex === 0 && itemContent.listStart > 1) {
    itemContent.listRestartPolite = itemContent.listStart;
  }
}

listRestartPolite is the right fit here because the restart only matters while the node is still the first item in that list. If later edits insert a new item before it, normalization can renumber naturally.

Verification

These checks passed:

bun test packages/markdown/src/lib/deserializer/deserializeMdList.spec.tsx
bun test packages/markdown/src
pnpm install
pnpm turbo build --filter=./packages/markdown
pnpm turbo typecheck --filter=./packages/markdown
pnpm lint:fix

Prevention

If a deserializer feeds nodes into a normalized list system, do not emit only the derived number field.

Emit the restart signal that normalization actually respects, then add one regression that runs the full path:

1. deserialize markdown
2. call editor.tf.setValue(...)
3. assert the restarted list still begins at the original number