feat: scaffold crate with alkcall 0.1.1 dependency

Empty module tree (adapters, client, gateway, server, websocket) matching
the AGENTS.md subsystem map. Features: h2/http1 (default), mcp (rmcp),
wss (tokio-tungstenite, for the from_wss consumer adapter).

Verified: cargo check (default), cargo check --all-features.

src/lib.rs

@@ -0,0 +1,9 @@
+//! alkhttp: HTTP interface for the alk stack — serves HTTP/1.1 + HTTP/2 on
+//! standard ALPNs (with WebSocket upgrade carrying the channels protocol)
+//! and hosts the HTTP-backed call-protocol adapters.
+
+pub mod adapters;
+pub mod client;
+pub mod gateway;
+pub mod server;
+pub mod websocket;