HTTP/1.1 parser with zero-copy design

[FumingPower3925]

Summary

Zero-alloc HTTP/1.1 request parser operating over []byte. Engine-agnostic (no I/O coupling).

Deliverables

• Method/path/version parsing (zero-copy slices into original buffer)
• Header parsing (case-insensitive lookup)
• Content-Length and chunked transfer-encoding body handling
• HTTP pipelining support (multiple requests in one buffer)
• SIMD-accelerated \r\n\r\n header terminator detection
• Port from old_celeris/internal/h1/parser.go

Tests

• Valid HTTP methods (GET, POST, PUT, DELETE, PATCH, HEAD, OPTIONS)
• HTTP/1.0 and HTTP/1.1 version parsing
• Pipelined requests (2+ requests in single buffer)
• Chunked transfer-encoding
• Malformed request rejection (bad method, missing version, oversized headers)
• 16MB header boundary enforcement
• Fuzz tests with random input

SDD Reference

Sections 4.3, 2.1

Dependencies

Depends on #1