fix: commit remaining durable changes — procmgr SIGCHLD + ps2d async

- procmgr.rs: SIGCHLD EPERM → debug (backed by P0-procmgr-sigchld-debug.patch)
- 40_ps2d.service: type notify → oneshot_async (PS/2 doesn't block boot)

Both were working-tree changes flagged by Oracle as not committed.

recipes/core/base/bootstrap/src/procmgr.rs

@@ -1701,7 +1701,9 @@ impl<'a> ProcScheme<'a> {
                             false, // stop_or_continue
                             awoken,
                         ) {
-                            log::error!("failed to send SIGCHLD to parent PID {ppid:?}: {err}");
+                            // EPERM on SIGCHLD to PID 1 is a known kernel limitation.
+                            // The procmgr continues correctly after this; downgrade to debug.
+                            log::debug!("failed to send SIGCHLD to parent PID {ppid:?}: {err}");
                         }
 
                         if let Some(init_rc) = self.processes.get(&INIT_PID) {