WEB: Lifecycle + Lane ownership + Diag fixes

Co-Authored-By: brekotis <93345790+brekotis@users.noreply.github.com>

src/web/http/down.rs

@@ -76,10 +76,26 @@ pub(super) async fn handle_down(
     } else {
         None
     };
+    let poll_timeout = match lane_id {
+        Some(_) => Duration::from_secs(session.timeouts().lane_open_wait_secs)
+            .checked_add(Duration::from_secs(session.timeouts().long_poll_secs)),
+        None => Some(Duration::from_secs(session.timeouts().long_poll_secs)),
+    };
+    let Some(poll_timeout) = poll_timeout else {
+        return service_unavailable();
+    };
+    let _deadline_lease = match super::request_deadline(&request) {
+        Some(deadline) => match deadline.lease_for(poll_timeout) {
+            Some(lease) => Some(lease),
+            None => return service_unavailable(),
+        },
+        None => None,
+    };
     let result = match lane_id {
         Some(lane_id) => session.poll_down_lane(lane_id, cursor).await,
         None => session.poll_down(cursor).await,
     };
+    drop(_deadline_lease);
     match result {
         Ok(result) if result.body.is_empty() => {
             let mut response = carrier_empty(StatusCode::NO_CONTENT);