Slate v2 Op-family Second Slice

Supporting plan. For current queue and roadmap truth, see master-roadmap.md.

Goal

• Land the next honest slate op-family slice: path-based set_node and Transforms.setNodes(...).

Finding

• The current docs already described set_node and Transforms.setNodes(...).
• The package still lacked both the operation and the transform wrapper.
• The deeper bug was worse: the draft/snapshot model stripped custom node props entirely, so a fake setNodes wrapper would have lied.

Slice

• Add real set_node support in the core transaction engine.
• Add path-based Transforms.setNodes(editor, props, { at }).
• Preserve custom element/text props through:
  • replacement
  • draft mutation
  • snapshot publication
  • text splitting/fragment cloning paths touched by the current proof subset
• Keep the slice narrow:
  • no broad legacy NodeOptions parity
  • no unsetNodes(...)
  • no wider node-family rollout

Verification

• yarn mocha --require ./config/babel/register.cjs ./packages/slate/test/snapshot-contract.ts
• yarn test:mocha
• yarn workspace slate-react run test
• targeted tsc diagnostics on changed packages/slate files: 0 errors
• targeted yarn exec eslint on changed packages/slate files
• yarn prettier --check on changed slate-v2 files
• pnpm exec prettier --check on changed plate-2 docs

Notes

• repo-wide yarn lint:typescript still hits stale workspace *-v2 tsconfig refs outside this slice
• repo-wide yarn lint:eslint still reports unrelated existing issues, so targeted eslint is the honest signal here