ci: enhance Jenkinsfile SSH retry/port and add runner process cleanup

Jenkinsfile

@@ -52,7 +52,7 @@ pipeline {
                                         returnStdout: true
                                     ).trim()
                                 } catch (Exception e) {
-                                    echo "⚠️ Temporary SSH network timeout / glitch. Retrying in 10s..."
+                                    echo "⚠️ Temporary SSH network timeout / glitch (${e.getMessage()}). Retrying in 10s..."
                                     sleep 10
                                     return false
                                 }