fix: preserve session layouts across shutdown and restore failures (#4400)

* fix: preserve session layouts across shutdown and restore failures

refs #4320

* test: update subscription fixture for pane restore errors

---------

Co-authored-by: JJ Liebig <jonathan.liebig@gmail.com>

1 files changed, 30 insertions, 0 deletions

diff --git a/src/platform/mod.rs b/src/platform/mod.rs
index 2ba3e6f3..488c5bee 100644
--- a/src/platform/mod.rs
+++ b/src/platform/mod.rs
@@ -3,6 +3,36 @@
 //! Centralizes OS-dependent behavior behind a clean boundary so core
 //! modules don't scatter `#[cfg]` branches through product logic.
 
+pub(crate) struct HostShutdownMonitor {
+    task: Option<tokio::task::JoinHandle<()>>,
+}
+
+impl HostShutdownMonitor {
+    pub(crate) fn start(
+        requested: std::sync::Arc<std::sync::atomic::AtomicBool>,
+        wake: impl Fn() + Send + Sync + 'static,
+    ) -> Self {
+        let task = monitor_host_shutdown(requested, wake);
+        Self { task }
+    }
+}
+
+impl Drop for HostShutdownMonitor {
+    fn drop(&mut self) {
+        if let Some(task) = self.task.take() {
+            task.abort();
+        }
+    }
+}
+
+#[cfg(not(target_os = "linux"))]
+fn monitor_host_shutdown(
+    _requested: std::sync::Arc<std::sync::atomic::AtomicBool>,
+    _wake: impl Fn() + Send + Sync + 'static,
+) -> Option<tokio::task::JoinHandle<()>> {
+    None
+}
+
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub struct ForegroundProcess {
     pub pid: u32,