Inspects structural properties first (err.code, err.cause.code, err.name),
falls back to message substring matching only when structure isn't enough.
Handles node-fetch FetchError, native fetch/undici TypeError + cause chain,
browser TypeError, Deno, and Bun error shapes.
Cross-runtime transport error classifier.
Inspects structural properties first (err.code, err.cause.code, err.name), falls back to message substring matching only when structure isn't enough. Handles node-fetch FetchError, native fetch/undici TypeError + cause chain, browser TypeError, Deno, and Bun error shapes.