Slate v2 wrapNodes should compose insert and move to preserve ids

What happened

The next broader node-structure slice after the narrow split/merge work was wrapNodes(...).

The tempting lie was to implement wrapping by cloning the wrapped node into a new wrapper tree.

That would have thrown away the original node id and quietly broken the same runtime-id guarantees the earlier slices had just proved.

What fixed it

The honest exact-path cut composes existing structural seams:

1. insert an empty wrapper at the target path
2. move the original node into that wrapper

That keeps the wrapped node as the same logical node:

• same runtime id
• new path
• wrapper gets the fresh id

Reusable rule

For Slate v2 structural wrapper helpers:

• prefer composing existing structural ops when that preserves node identity
• do not clone-and-reinsert if the node is supposed to remain the same logical node

If wrapNodes(...) breaks the wrapped node id, it is not wrapping. It is replacing.