feat: add inherited sessions and desktop session teardown

programs/man/syscalls.2

@@ -65,6 +65,16 @@
     Terminate another process by PID.
         int montauk::kill(int pid);
 
+.B SYS_SETSESSION (174)
+    Make the calling process the leader of a new process session. Processes
+    spawned afterward inherit the session identifier.
+        int montauk::setsession();
+
+.B SYS_KILLSESSION (175)
+    Terminate all live processes in a process session. Returns the number of
+    members signalled; repeat until zero to wait for complete teardown.
+        int montauk::killsession(int sessionId);
+
 .B SYS_CHDIR (96)
     Change the calling process's current working directory.
         int montauk::chdir(const char* path);