port(smarm): track HEAD efbc254 — RFC 014/015 API sync

- gen_server rename (RFC 015, 3e31606): ServerRef/ServerCtx/ServerBuilder
  -> GenServerRef/GenServerCtx/GenServerBuilder across conn_actor,
  conn_registry, serve, pubsub, channels::session.
- type Timer = () on the three GenServer impls (RFC 015, 57eadb5);
  handle_timer/handle_idle/tick_every stay defaulted — opt-in later.
- Watcher and GenServerCtx are now generic over the server type: watcher
  fields typed Watcher<Table<M>> / Watcher<Registry<P, K>>; Registry's
  struct bounds strengthened to its GenServer impl bounds
  (P: Encode + Decode + Send + Sync + 'static, K: SessionKey) so the
  Watcher field's G: GenServer bound is satisfiable at the declaration.
- RFC 014 (a866e34) registry: register is (Name<M>, Sender<M>), self-only
  — a name is a typed messaging endpoint, not a pid tag. The
  introspection-only urus.server / urus.listener.{i} bindings are dropped
  rather than faked with unit channels; the whereis integration test is
  deleted; a proper messageable-name design is icebox'd in ROADMAP.md.
- Audit vs smarm 6c2b7e9 (queued messages dropped when Receiver drops):
  pubsub's prune-on-send-failure retain still holds — send Errs once
  receiver_alive is false, so a dropped rx prunes on next broadcast,
  exactly what subscriber_count's doc already promised. Freeing stranded
  Arc<M> broadcasts is strictly good. No change needed.
- The 7x E0283 in channels/mod.rs were cascade fallout of the generics
  changes; dissolved with the port, as discovery predicted.

Suite: 90 lib + 45 integration + 2 doc, green under default, smarm-trace,
phoenix, and all-features. 3 pre-existing clippy lints (conn.rs,
parser.rs, conn_actor.rs; clippy 1.97 strictness) deferred to a follow-up
chore commit to keep this diff pure.

tests/integration.rs

@@ -89,24 +89,9 @@ fn hello_world() {
     assert_eq!(http_body(&resp), b"hello urus");
 }
 
-#[test]
-fn server_and_listeners_are_registered() {
-    // `whereis` must run inside the runtime (the test itself is a foreign
-    // OS thread with no runtime in its TLS), so probe from a handler —
-    // connection actors live in the runtime by construction.
-    let pipe = Pipeline::new().plug(
-        Router::new().get("/whereis", |c: Conn, _n: Next| {
-            let ok = smarm::whereis("urus.server").is_some()
-                && smarm::whereis("urus.listener.0").is_some()
-                && smarm::whereis("urus.listener.1").is_some(); // pool of 2
-            c.put_status(200).put_body(if ok { "registered" } else { "missing" })
-        })
-    );
-    let port = spawn_server(pipe);
-    let resp = send_request(port, b"GET /whereis HTTP/1.1\r\nHost: x\r\nConnection: close\r\n\r\n");
-    assert_eq!(http_status(&resp), 200);
-    assert_eq!(http_body(&resp), b"registered");
-}
+// `server_and_listeners_are_registered` was deleted with the RFC 014 port:
+// urus no longer binds `urus.server` / `urus.listener.{i}` names (see the
+// note in serve.rs and the icebox entry in ROADMAP.md).
 
 #[test]
 fn echo_body() {