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/mod.rs

@@ -18,8 +18,9 @@ pub use byte_adapter::{
 
 #[cfg(any(test, feature = "wss"))]
 pub use byte_adapter::split_tungstenite_to_bytes;
-#[cfg(feature = "wss")]
-pub(crate) use byte_adapter::wait_for_eof;
+#[cfg(any(test, feature = "wss"))]
+#[allow(unused_imports)]
+pub(crate) use upgrade::adapter_install_channel_zero;
 pub use upgrade::{run_channels_session, ws_bearer_auth, ws_upgrade_handler};
 
 #[cfg(any(test, feature = "test-support"))]