Adds the `tokio::net::TcpStream`-specialised async constructor that
owns the full transport-bring-up sequence:
TCP connect → NMF preamble → DH Connect → AuthenticateMe (one-way)
Signature:
```
async fn connect(
endpoint: SocketAddr,
passphrase: &str,
crypto_parameters: &CryptoParameters,
via_uri: impl Into<String>,
connection_id: [u8; 16],
) -> Result<(AsbTransport<TcpStream>, ConnectResponse), Error>
```
Returns the `ConnectResponse` alongside the transport so callers can
inspect the negotiated `connection_lifetime` (the `:V2` suffix
toggles Apollo vs Baktun encryption — see F23).
New error variant: `ConnectionError::TransportFailure { detail }`
covers all transport-bring-up failure modes (NMF / NBFX / auth /
peer Fault). The underlying error type is intentionally erased to
keep the public taxonomy small; `detail` carries the Display
representation.
Errors are mapped at the AsbClient / AuthError boundary via private
`map_client_error` / `map_auth_error` helpers.
1 new test:
* `connect_to_unreachable_endpoint_surfaces_connection_error` — TCP
connect to 127.0.0.1:1 (TCPMUX-reserved) cleanly errors without
panicking. Smoke test for the constructor signature + error path.
Stubbed for F26 step 3:
* `Session::connect_asb` constructor — the SessionInner refactor to
host both NMX + ASB transports under one struct is heavier than
this iteration's scope.
* Operation-routing layer that maps ASB result types (ItemStatus,
RuntimeValue) back to mxaccess types (MxStatus, DataChange,
MxValue).
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Joseph Doherty
14bb5297a8