Slate v2 Op-family Fifteenth Slice

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

Goal

• Land the exact-path structural counterpart after wrapNodes(...) and unwrapNodes(...): a narrow liftNodes(...) cut.

Scope

• Start with exact path-based lifting only.
• Start with element nodes only.
• Support the honest exact structural cases:
  • only child
  • first child
  • middle child
  • last child
• Avoid match/mode/selection/void parity in this slice.

Phases

• Confirm the exact path lift semantics and current structural seams
• Write focused failing tests
• Implement the smallest honest core/API slice
• Sync package/public docs
• Verify the touched package/docs