_fast_h1

Fast HTTP/1.1 parser for the sync worker — replaces h11 on the hot path.

Parses request lines and headers directly from bytes using split/index operations (~3 µs vs ~22 µs for h11) while enforcing the same safety checks that matter for real-world deployment:

• Method validation (rejects unknown methods)
• Header size limit (prevents memory exhaustion)
• Null byte / control character injection in targets and header names
• Duplicate Content-Length detection (request smuggling vector)
• Content-Length + Transfer-Encoding conflict (RFC 7230 §3.3.3)
• Negative or non-numeric Content-Length rejection
• Chunked Transfer-Encoding detection (returns flag so caller can handle)

Not a full HTTP parser — does not handle:

• Chunked body decoding (caller must handle or reject)
• Obs-fold header continuation lines (obsolete since RFC 7230)
• Trailer headers