Lexical list utility harvest rows need path ancestry contracts

Problem

Lexical list utility tests look tempting to port as helper APIs: $getListDepth, $getTopListNode, and $isLastItemInList.

That is the wrong target for Slate v2 unless Slate has accepted a public list helper API. The portable behavior is the tree fact those helpers expose.

Symptoms

• A harvest row says refactor-existing but the source test is mostly helper API shape.
• Copying the row would create a local list helper just to satisfy an upstream helper name.
• Existing Slate coverage already has broad transform/list behavior, but not a compact proof that public path queries expose the same ancestry facts.

What Didn't Work

• Treating the Lexical helper names as the behavior.
• Duplicating every source fixture depth. One, two, and five levels all test the same path ancestry mechanism.
• Routing the row to browser list tests. This is model/query behavior, not native input transport.

Solution

Write one compact package proof against Slate's public query primitives:

• Path.levels gives the logical ancestor chain.
• Node.get lets the proof filter list and list-item paths.
• Node.has(editor, Path.next(path)) distinguishes terminal and non-terminal sibling positions.

The proof belongs in .tmp/slate-v2/packages/slate/test/query-contract.ts.

Why This Works

Slate's raw model does not need Lexical's list helper API to preserve the behavior. The durable contract is that public path and node queries can recover:

• nested list depth;
• the top logical list ancestor, even below a non-root wrapper;
• descendant list ancestors for deeply nested items;
• whether an item is terminal in its local or ancestor list path.

Prevention

When harvesting list utility tests from another editor:

• reject upstream helper API shape unless Slate already owns that public API;
• map helper outputs to Path, Node, or Editor query contracts;
• add one mechanism-level package proof instead of one fixture per source depth;
• keep browser proof for native list input, paste, or selection transport only.