4649 listStart setValue

Goal

Keep ordered-list start values from markdown deserialization intact after editor.tf.setValue(...) so list rendering and markdown export can use the real numbering.

Source Of Truth

• GitHub issue: udecode/plate#4649
• Title: Editor SetValue stripping out listStart from deserialized Markdown breaking list rendering.
• Type: bug
• Expected outcome:
  • deserialized ordered lists keep listStart
  • setValue does not strip that field
  • list UI and markdown export can read the preserved value

Likely Seams

• packages/list/src/**
• packages/core/src/** if normalization strips unknown element props
• packages/markdown/src/** if deserializer shape is mismatched

Plan

1. Inspect current list element types, normalization, and markdown deserializer output shape.
2. Reproduce with the smallest behavior test around setValue.
3. Fix the ownership seam that drops listStart.
4. Verify with targeted tests, then package build/typecheck/lint for touched packages.
5. Decide whether a changeset is needed.

Findings

• Issue report says markdown deserialization already emits the correct listStart.
• The field disappears after editor.tf.setValue(...), so the likely bug is not parsing; it is normalization or node copying.
• Existing solution docs mention markdown list serializer bugs, but nothing yet on listStart loss through editor value setting.
• The real ownership seam is the list normalizer: a first item with listStart > 1 is only preserved when the node also carries listRestart or listRestartPolite.
• Markdown deserialization emitted listStart but not the restart metadata, so normalization stripped the first item of a restarted ordered list and renumbered following siblings incorrectly.

Progress

• Read issue #4649
• Read repo instructions
• Loaded planning + TDD guidance
• Checked existing docs/solutions for related prior fixes
• Added a regression spec covering deserializeMd(...) + editor.tf.setValue(...)
• Fixed ordered-list deserialization to add listRestartPolite on the first item of ordered lists that start above 1
• Verified with package tests, build, typecheck, and lint

Verification Targets

• Regression test that fails before the fix
• Targeted package test sweep for touched specs
• pnpm install
• pnpm turbo build --filter=...
• pnpm turbo typecheck --filter=...
• pnpm lint:fix