[exec.sysctxrepl.recvproxy] Create new subclause for receiver proxies

Fixes NB US 264-397 (C++26 CD).

Author: jensmaurer

source/exec.tex

@@ -8432,26 +8432,7 @@
 Facilities in the \tcode{system_context_replaceability} namespace
 allow users to replace the default implementation of \tcode{parallel_scheduler}.
 
-\rSec2[exec.sysctxrepl.query]{\tcode{query_parallel_scheduler_backend}}
-\indexlibraryglobal{query_parallel_scheduler_backend}%
-\begin{itemdecl}
-shared_ptr<parallel_scheduler_backend> query_parallel_scheduler_backend();
-\end{itemdecl}
-
-\begin{itemdescr}
-\pnum
-\tcode{query_parallel_scheduler_backend()} returns
-the implementation object for a parallel scheduler.
-
-\pnum
-\returns
-A non-null shared pointer to an object
-that implements the \tcode{parallel_scheduler_backend} interface.
-
-\pnum
-\remarks
-This function is replaceable\iref{dcl.fct.def.replace}.
-\end{itemdescr}
+\rSec2[exec.sysctxrepl.recvproxy]{Receiver proxies}
 
 \begin{codeblock}
 namespace std::execution::system_context_replaceability {
@@ -8524,6 +8505,27 @@
 for \tcode{get_stop_token_t}.
 \end{itemdescr}
 
+\rSec2[exec.sysctxrepl.query]{\tcode{query_parallel_scheduler_backend}}
+\indexlibraryglobal{query_parallel_scheduler_backend}%
+\begin{itemdecl}
+shared_ptr<parallel_scheduler_backend> query_parallel_scheduler_backend();
+\end{itemdecl}
+
+\begin{itemdescr}
+\pnum
+\tcode{query_parallel_scheduler_backend()} returns
+the implementation object for a parallel scheduler.
+
+\pnum
+\returns
+A non-null shared pointer to an object
+that implements the \tcode{parallel_scheduler_backend} interface.
+
+\pnum
+\remarks
+This function is replaceable\iref{dcl.fct.def.replace}.
+\end{itemdescr}
+
 \rSec2[exec.sysctxrepl.psb]{Class \tcode{parallel_scheduler_backend}}
 
 \begin{codeblock}