protocol: add river_window_manager_v1.exit_session

 protocol/river-window-management-v1.xml | 12 ++++++++++++
 river/WindowManager.zig                 |  4 ++++
 2 files changed, 16 insertions(+)

diff --git a/protocol/river-window-management-v1.xml b/protocol/river-window-management-v1.xml
index 34536dc..dd9e556 100644
--- a/protocol/river-window-management-v1.xml
+++ b/protocol/river-window-management-v1.xml
@@ -305,6 +305,18 @@
       <arg name="surface" type="object" interface="wl_surface"
         summary="base surface"/>
     </request>
+
+    <request name="exit_session" since="4">
+      <description summary="exit the Wayland session">
+        End the current Wayland session and exit the compositor.
+        All Wayland clients running in the current session, including
+        the window manager, will be disconnected.
+
+        Window managers should only make this request if the user explicitly
+        asks to exit the Wayland session, not for example on normal window
+        manager termination.
+      </description>
+    </request>
   </interface>
 
   <interface name="river_window_v1" version="4">
diff --git a/river/WindowManager.zig b/river/WindowManager.zig
index 4c3a340..011cd2a 100644
--- a/river/WindowManager.zig
+++ b/river/WindowManager.zig
@@ -187,6 +187,10 @@ fn handleRequest(
                 return;
             };
         },
+        .exit_session => {
+            log.info("window manager requested to exit session", .{});
+            server.wl_server.terminate();
+        },
     }
 }