fix(ci): make signal probe portable and gate Linux initialization

Signed-off-by: Drew Newberry <anewberry@nvidia.com>

Author: drew

crates/openshell-cli/src/ssh.rs

@@ -2230,6 +2230,18 @@ mod tests {
         }
     }
 
+    #[cfg(target_os = "linux")]
+    #[test]
+    fn interactive_signal_workload_child() {
+        let Some(marker) = std::env::var_os("OPENSHELL_SIGNAL_WAIT_MARKER") else {
+            return;
+        };
+        // Only publish readiness after exec has reset the parent's caught
+        // signal dispositions. No external utility filename is assumed.
+        fs::write(marker, std::process::id().to_string()).unwrap();
+        std::thread::sleep(Duration::from_secs(30));
+    }
+
     #[cfg(target_os = "linux")]
     #[test]
     fn interactive_signal_wait_child() {
@@ -2238,12 +2250,14 @@ mod tests {
         };
         let mut command = Command::new("sh");
         command
+            .args(["-c", "ulimit -c 0; exec \"$@\"", "signal-probe"])
+            .arg(std::env::current_exe().unwrap())
             .args([
-                "-c",
-                "ulimit -c 0; printf '%s' $$ > \"$1\"; exec sleep 30",
-                "signal-probe",
+                "--exact",
+                "ssh::tests::interactive_signal_workload_child",
+                "--nocapture",
             ])
-            .arg(marker)
+            .env("OPENSHELL_SIGNAL_WAIT_MARKER", marker)
             .stdin(Stdio::inherit());
         let runtime = tokio::runtime::Builder::new_current_thread()
             .enable_all()
@@ -2287,8 +2301,7 @@ mod tests {
             let deadline = Instant::now() + Duration::from_secs(10);
             loop {
                 if let Ok(pid) = fs::read_to_string(&marker)
-                    && let Ok(executable) = fs::read_link(format!("/proc/{pid}/exe"))
-                    && executable.file_name().is_some_and(|name| name == "sleep")
+                    && pid.parse::<u32>().is_ok()
                 {
                     break;
                 }

crates/openshell-sandbox/src/process.rs

@@ -232,6 +232,7 @@ fn apply_canonical_process_environment(
 
 static BOUNDARY_USER_ENVIRONMENT: OnceLock<HashMap<String, String>> = OnceLock::new();
 
+#[cfg(target_os = "linux")]
 pub(crate) fn install_boundary_user_environment(
     environment: HashMap<String, String>,
 ) -> Result<(), String> {