HyperHTTP 2.0.0

Added

• Custom zero-copy asyncio.Protocol (FastStream) for the HTTP/1.1 hot path,
  bypassing asyncio.StreamReader and removing intermediate buffer copies.
• HTTP/2 connection probing that serializes the first TLS handshake per host so
  concurrent requests multiplex onto a single H2 connection instead of racing to
  open several.
• Optional speed extras: orjson, uvloop, h11, brotli, zstandard
  (installable via pip install 'hyperhttp[speed]').
• Streaming response API (aiter_bytes, aiter_lines, aread) with strict
  Content-Length validation.
• DNS cache with Happy Eyeballs-style dual-stack connect.
• Integration test suite covering HTTP/1.1, HTTP/2, TLS, redirects, framing
  edge cases, retries, and circuit breaker behavior.

Changed

• Breaking: full rewrite of the client, connection pool, HTTP/1 parser,
  buffer pool, and H2 multiplexer. Public API surface is smaller and
  intentionally incompatible with 1.x.
• Response.aread now collects raw chunks and joins once with b"".join,
  halving memcpy work for identity-encoded bodies with a known length.
• Socket tuning: SO_RCVBUF=2 MiB, SO_SNDBUF=1 MiB, TCP_NODELAY,
  SO_KEEPALIVE enabled by default.
• Error classifier rewritten to map hyperhttp's own exception hierarchy to
  retry / circuit-breaker categories.

Removed

• Breaking: legacy connection manager, old HTTP/1 and HTTP/2 protocol
  modules, and the pre-2.0 test suite.
• setup.py (packaging driven entirely by pyproject.toml).

Fixed

• HTTP/1.1 framing: reject responses with conflicting Content-Length and
  Transfer-Encoding, or multiple Content-Length headers.
• Body truncation now raises RemoteProtocolError instead of returning a
  short body silently.