Create /run/reboot-required by default

When staging a new deployment, create /run/reboot-required to signal that
a reboot is needed. This file is monitored by kured (Kubernetes Reboot
Daemon) and other tools to detect when a system needs to be rebooted.

This makes it easier to integrate bootc with kured and similar tools
without requiring manual configuration or bridging.

Author: gursewak1997

lib/src/deploy.rs

@@ -737,6 +737,13 @@ pub(crate) async fn stage(
     })
     .await;
 
+    // Create /run/reboot-required to signal that a reboot is needed
+    // This file is monitored by kured (Kubernetes Reboot Daemon)
+    let run_dir = Dir::open_ambient_dir("/run", cap_std::ambient_authority())?;
+    if !run_dir.try_exists("reboot-required")? {
+        run_dir.atomic_write("reboot-required", b"").context("Creating /run/reboot-required")?;
+    }
+
     Ok(())
 }