split By Path
Splits the tree at the given path.
Lowers to a single editInternal call with splitLevel = 1 at the resolved position — no node is copied or deleted; the split is produced by CrdtTree.edit's own split step. Mirrors JS document/json/tree.ts splitByPath (v0.7.23).
Throws
with ErrInvalidArgument if path is empty, resolves to the root node (a text node's element parent with no parent of its own, or an element node with no parent), or resolves to an index inside a UTF-16 surrogate pair.