feat: expose Server.port (#6)

* feat: report the port a server is listening on

`TcpTransport` took a port and told nobody what it did with it, so
`port=0` bound an ephemeral port that nothing could discover.

`Server.port` now reports it. To make the assigned port knowable, the
listener binds in `start()` rather than in the accept task it spawns —
the bound address doesn't exist until something calls `local_addr`, and
nothing could, from inside a task that had already been handed off.

* review: keep the field named port, drop the redundant comments

* docs: restore the TcpClient max_inflight_msgs note

* chore: release 0.2.1

feat: optional CUDA host-memory pinning of the ring buffers (#5)

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

chore: bump version to 0.1.1

The v0.1.1 release tag was created without bumping the version in
pyproject.toml or Cargo.toml, so the release workflow built 0.1.0
wheels and PyPI rejected them as duplicates.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

fix: docs workflow (#2)

* fix: docs workflow

* chore: remove dtolnay/rust-toolchain in favour of rustup