Collect every descendant of `node` whose `kind` equals `kind`. Unconditional full descent -- does NOT stop at function-like boundaries. Callers that need boundary-stopping behavior (e.g. "only look inside this function, not nested ones") should use `findFirstDescendant` with a predicate that encodes that boundary instead. depth-first document order. Empty array if none found.

Depth-first search for the first descendant of `node` matching `predicate`. Short-circuits on first match -- does not continue walking siblings/children once found. An optional `stopAt` predicate lets the caller prune descent into a subtree (checked only when `predicate` did not already match on that same node) -- e.g. to stop at nested function boundaries the way `extractor.js`'s original `hasReturnWithValue` did. Omit it for unconditional full descent. a non-matching node, its children are not visited. `undefined` if none found.

Narrow `node` to a class declaration, or return `null`. Thin wrapper over `ts.isClassDeclaration` -- exists purely to cut the `ts.isClassDeclaration(node) ? node : null` boilerplate at call sites.

Narrow `node` to a function-like expression, or return `null`. Matches exactly the set lib/extractor.js's own `isFunctionLike()` already treats as function-like: arrow functions and function expressions (NOT function declarations, which extractor.js handles as a separate case).