feat(websocket): WsTimeouts request extension for WS pump knobs (WS-17)

- WsTimeouts { idle, write } request extension mirrors ChannelsPolicy:
  a deployment layers it on a WS route (bare-registry routes included)
  to set the pump knobs per route
- precedence: extension present replaces the router state entirely;
  absent falls back to SessionState (adapter-configured idle) and the
  crate default write window — a Default impl never clobbers the
  adapter-configured idle knob
- upgrade.rs module + handler docs now state the real defaults for
  bare-registry routes (60 s idle + 60 s write, 64-session semaphore,
  handler-private WsSessions) and the extension surface
- split_ws_to_bytes_idle_with_write exposes the WS-18 write window to
  run_channels_session; acceptance test drives a bare-registry route
  with a 150 ms extension idle window (1001 eviction observed)

Verification: scripts/verify.sh OK (343 passed), test-support suite
ok, clippy -D warnings clean, fmt clean

src/websocket/byte_adapter.rs

@@ -655,10 +655,25 @@ pub fn split_ws_to_bytes(socket: WebSocket) -> (WsByteStream, WsPumps) {
 /// adapter is the single seam between axum's WS and alkcall's
 /// byte-oriented channels machinery; shared with `from_wss`.
 /// `idle_timeout` (WS-01): `None` = no idle bound, `Some(d)` closes
-/// the read with 1001 after `d` without an inbound WS message.
+/// the read with 1001 after `d` without inbound chunk progress. The
+/// write pump runs with [`crate::websocket::DEFAULT_WS_WRITE_TIMEOUT`]
+/// — see [`split_ws_to_bytes_idle_with_write`] for the WS-18
+/// configurable form.
 pub fn split_ws_to_bytes_idle(
     socket: WebSocket,
     idle_timeout: Option<Duration>,
+) -> (WsByteStream, WsPumps) {
+    split_ws_to_bytes_idle_with_write(socket, idle_timeout, None)
+}
+
+/// [`split_ws_to_bytes_idle`] with an explicit WS-18 write-progress
+/// window: `None` = the crate default
+/// ([`DEFAULT_WS_WRITE_TIMEOUT`](crate::websocket::DEFAULT_WS_WRITE_TIMEOUT)),
+/// `Some(d)` a deployment-set window.
+pub fn split_ws_to_bytes_idle_with_write(
+    socket: WebSocket,
+    idle_timeout: Option<Duration>,
+    write_timeout: Option<Duration>,
 ) -> (WsByteStream, WsPumps) {
     let (ws_sink, ws_stream) = socket.split();
     let (read_tx, read_rx) = mpsc::channel::<Vec<u8>>(READ_SLOTS);
@@ -690,7 +705,7 @@ pub fn split_ws_to_bytes_idle(
         ws_sink,
         write_rx,
         write_error_slot,
-        Some(crate::websocket::DEFAULT_WS_WRITE_TIMEOUT),
+        Some(write_timeout.unwrap_or(crate::websocket::DEFAULT_WS_WRITE_TIMEOUT)),
     ));
 
     (