fix(websocket): lossless EOF signal + pending sweep (WS-02, CON-02)

- Replace the axum/tungstenite pump paths' Notify-based read-EOF signal
  with a retained tokio watch channel: a late subscriber (monitor
  spawned after session setup, or pump EOF before the receiver is
  taken) still observes EOF (WS-02).
- from_wss drop monitor: on EOF (or session close) fail all pendings
  retryable, then keep sweeping the pending map every 1 s — calls
  registered after the initial fail_all (the forgotten-session import
  path) resolve instead of hanging (CON-02).
- Tests: drop-during-registration race variants (forget + held
  session) and a post-EOF registration resolved via the sweep; the
  existing no-hang test stays green.

cargo test (219), cargo test --features wss (231, 3x for flake check),
cargo clippy --all-targets -- -D warnings, cargo fmt --check

src/websocket/byte_adapter.rs

@@ -95,33 +95,13 @@ impl WsPumps {
     /// EOF signaled at any point — including before the receiver is
     /// taken or the observer starts awaiting — is still observed, and
     /// may be observed repeatedly. Used by `from_wss`'s
-    /// connection-drop monitor (ADR-070); await it with
-    /// [`wait_for_eof`].
+    /// connection-drop monitor (ADR-070).
     #[cfg(feature = "wss")]
     pub(crate) fn read_eof(&self) -> tokio::sync::watch::Receiver<bool> {
         self.read_eof.subscribe()
     }
 }
 
-/// Resolves once the given WS read-EOF watch receiver observes `true`.
-///
-/// Lossless by construction: a `watch::Receiver` retains the latest
-/// value, so an EOF signaled before this call (or before the receiver
-/// existed) is still observed — the property a one-shot `Notify` lacked
-/// (WS-02). Returns early (treated as EOF) if the sender half is
-/// dropped, e.g. the read pump was aborted.
-#[cfg(feature = "wss")]
-pub(crate) async fn wait_for_eof(rx: &mut tokio::sync::watch::Receiver<bool>) {
-    loop {
-        if *rx.borrow_and_update() {
-            return;
-        }
-        if rx.changed().await.is_err() {
-            return;
-        }
-    }
-}
-
 /// Split a `WebSocket` into the byte stream + the pump tasks. The
 /// adapter is the single seam between axum's WS and alkcall's
 /// byte-oriented channels machinery; shared with `from_wss`.