Classify a thrown value as a transport-level error.
Inspects structural properties first (err.code, err.cause.code, err.name),
then falls back to message substring matching. Handles node-fetch FetchError,
native fetch/undici TypeError + cause chain, browser TypeError, Deno, and Bun.
Classify a thrown value as a transport-level error.
Inspects structural properties first (err.code, err.cause.code, err.name), then falls back to message substring matching. Handles node-fetch FetchError, native fetch/undici TypeError + cause chain, browser TypeError, Deno, and Bun.