Picks up zzstoatzz/websocket.zig#1: streaming Handshake.parse onto std.http.HeadParser plus RFC 7230 strictness. Fixes the recurring class of TCP-fragmentation parser bugs by replacing the one-shot buffer matcher with a stdlib SIMD streaming state machine. Two new error variants from the upstream parser: error.WhitespaceBeforeColon (RFC 7230 §3.2) error.AmbiguousBodyLength (RFC 7230 §3.3) Both manifest as 400 responses; downstreams that switch on Handshake.parse errors should add arms for these if they want specific handling, otherwise they fall through to the generic 400 path. Co-Authored-By: Claude Opus 4 (1M context) <noreply@anthropic.com>