cmd/tsconnect: close the SSH session an unload event instead of beforeunload

The window may not end up getting unloaded (if other beforeunload
handlers prevent the event), thus we should only close the SSH session
if it's truly getting unloaded.

Updates tailscale/corp#7304

Signed-off-by: Mihai Parparita <mihai@tailscale.com>

cmd/tsconnect/src/lib/ssh.ts

@@ -42,7 +42,7 @@ export function runSSHSession(
   term.focus()
 
   let resizeObserver: ResizeObserver | undefined
-  let handleBeforeUnload: ((e: BeforeUnloadEvent) => void) | undefined
+  let handleUnload: ((e: Event) => void) | undefined
 
   const sshSession = ipn.ssh(def.hostname, def.username, {
     writeFn(input) {
@@ -60,8 +60,8 @@ export function runSSHSession(
     onDone() {
       resizeObserver?.disconnect()
       term.dispose()
-      if (handleBeforeUnload) {
-        parentWindow.removeEventListener("beforeunload", handleBeforeUnload)
+      if (handleUnload) {
+        parentWindow.removeEventListener("unload", handleUnload)
       }
       onDone()
     },
@@ -75,6 +75,6 @@ export function runSSHSession(
 
   // Close the session if the user closes the window without an explicit
   // exit.
-  handleBeforeUnload = () => sshSession.close()
-  parentWindow.addEventListener("beforeunload", handleBeforeUnload)
+  handleUnload = () => sshSession.close()
+  parentWindow.addEventListener("unload", handleUnload)
 }