fix: count ptmx master fds under devpts layouts (#1984)

live_server_holds_one_pty_master_fd_per_pane counted only /proc/<pid>/fd links
resolving to exactly /dev/ptmx. On devpts setups such as WSL2 and many
containers, a PTY master fd resolves to /dev/pts/ptmx instead, so the test found
zero masters and failed with "had 0 ptmx master fds; expected 1" even though the
server held the pane's master fd. Match both ptmx node paths; pty slaves still
resolve to /dev/pts/<N> and stay uncounted, so the one-master-per-pane invariant
is unchanged.

1 files changed, 3 insertions, 2 deletions

diff --git a/tests/live_handoff.rs b/tests/live_handoff.rs
index 4d81246a..832079e8 100644
--- a/tests/live_handoff.rs
+++ b/tests/live_handoff.rs
@@ -414,7 +414,8 @@ fn server_ptmx_fd_count(pid: u32) -> usize {
     entries
         .filter_map(Result::ok)
         .filter_map(|entry| fs::read_link(entry.path()).ok())
-        .filter(|target| target == Path::new("/dev/ptmx"))
+        // ptmx master node: /dev/ptmx or /dev/pts/ptmx (devpts); slaves /dev/pts/<N> excluded.
+        .filter(|target| target == Path::new("/dev/ptmx") || target == Path::new("/dev/pts/ptmx"))
         .count()
 }
 
@@ -443,7 +444,7 @@ fn wait_for_server_ptmx_fd_count(pid: u32, expected: usize, timeout: Duration) {
         }
         thread::sleep(Duration::from_millis(25));
     }
-    panic!("server pid {pid} had {last_count} /dev/ptmx fds; expected {expected}");
+    panic!("server pid {pid} had {last_count} ptmx master fds; expected {expected}");
 }
 
 #[cfg(target_os = "linux")]