docs(arch): AlknetClient native dial seam — resolves OQ-55 (ADR-089)

Extract the deferred AlknetClient as a new crate alknet-client — the
client-side analogue of AlknetEndpoint. Three dial methods (QUIC +
TCP+TLS via TlsClientConfig, iroh via key) produce a Connection for
CallClient::spawn_dispatch / ChannelClient::from_connection to consume.
The deferral collapsed because ADR-086 gave the native endpoint type
three dial shapes within one endpoint type, ADR-087 broke the circular
hedge, and ADR-083 gave the server-side shape to mirror by symmetry.

Names the three concept layers that were tangled throughout the initial
development (deployment role / establishment side / ALPN-level category)
so the fix is legible. Names alknet/register as a dialable entry-point
ALPN (native registration, parallel to HTTP registration in OQ-58); its
wire protocol is deferred to OQ-66 (blocked on OQ-58's token model).

Cross-references updated across 11 existing docs (README, overview,
open-questions, OQ-55, tls, hub, core, channels README/overview/
channel-client, call client-and-adapters) to reflect OQ-55 resolved and
the new alknet-client crate. Architecture review passed (2 critical, 7
warnings — all addressed).

docs/architecture/crates/call/client-and-adapters.md

@@ -130,7 +130,9 @@ impl CallClient {
     /// Feature-gated on `quinn` (the dial is QUIC-specific). Additive
     /// and two-way-door — `connect_tcp_tls`, `connect_webtransport`,
     /// etc. join it as transports are added, without touching the
-    /// `spawn_dispatch` contract.
+    /// `spawn_dispatch` contract. This convenience is a thin wrapper
+    /// over `AlknetClient::dial_quic` (ADR-089) — a caller that needs
+    /// transport selection uses `AlknetClient` directly.
     #[cfg(feature = "quinn")]
     pub async fn connect(
         &self,