Pull node-resolution logic out of dial/dialTLS into pure resolveHTTPNode
and resolveTLSNode helpers. This separates node selection (bypass, hop,
fallback) from connection establishment, making both independently
testable. Add 21 new tests covering bypass, hop selection, nil-hop,
addr fallback, upgrade response type mismatch, websocket frames,
response body rewriting, and h2 preface validation.
ginuerzh
3646c23398