fix(cloudlab): quote ssh arguments in on_nodes (SC2068)

cloudlab/bin/on_nodes

@@ -25,5 +25,5 @@ for ((i = $first ; i <= $last; i++)); do
     node=node$i
     echo ""
     echo $node:
-    ssh -4 $node $@
-done
+    ssh -4 "$node" "$@"
+done

cloudlab/tests/on_nodes.bats

@@ -0,0 +1,80 @@
+#!/usr/bin/env bats
+
+# SPDX-License-Identifier: BSD-1-Clause
+#
+# Regression tests for cloudlab/bin/on_nodes.
+#
+# These document the SC2068 fix: the remote command and its arguments
+# must be forwarded to ssh with their word boundaries intact, which
+# requires "$@" (quoted) rather than a bare $@. With an unquoted $@ an
+# argument containing spaces or glob characters is re-split / expanded by
+# the loop's word splitting before ssh ever sees it.
+#
+# Run:  nix shell nixpkgs#bats -c bats cloudlab/tests/on_nodes.bats
+#
+# No new CI is wired; this file is included as executable documentation.
+
+setup() {
+    ON_NODES="${BATS_TEST_DIRNAME}/../bin/on_nodes"
+
+    # Stub PATH with a fake ssh that records exactly the argv it receives,
+    # one argument per line, so tests can assert on argument boundaries.
+    STUB_DIR="$(mktemp -d)"
+    ARGV_LOG="${STUB_DIR}/argv.log"
+    cat > "${STUB_DIR}/ssh" <<EOF
+#!/usr/bin/env bash
+: > "${ARGV_LOG}"
+for a in "\$@"; do
+    printf '%s\n' "\$a" >> "${ARGV_LOG}"
+done
+EOF
+    chmod +x "${STUB_DIR}/ssh"
+    PATH="${STUB_DIR}:${PATH}"
+}
+
+teardown() {
+    rm -rf "${STUB_DIR}"
+}
+
+# Argument count that ssh saw, minus the leading `-4 nodeN` (2 args).
+forwarded_count() {
+    echo $(( $(wc -l < "${ARGV_LOG}") - 2 ))
+}
+
+@test "usage error when fewer than 3 args" {
+    run "$ON_NODES" 1
+    [ "$status" -eq 1 ]
+    [[ "$output" == Usage:* ]]
+}
+
+@test "simple command is forwarded verbatim" {
+    run "$ON_NODES" 1 1 echo hello
+    [ "$status" -eq 0 ]
+    # ssh argv: -4 node1 echo hello
+    run cat "${ARGV_LOG}"
+    [ "${lines[0]}" = "-4" ]
+    [ "${lines[1]}" = "node1" ]
+    [ "${lines[2]}" = "echo" ]
+    [ "${lines[3]}" = "hello" ]
+}
+
+@test "argument containing spaces stays a single argument" {
+    "$ON_NODES" 1 1 echo "one two three"
+    # 2 forwarded args: 'echo' and 'one two three' (NOT split into 4).
+    [ "$(forwarded_count)" -eq 2 ]
+    run cat "${ARGV_LOG}"
+    [ "${lines[3]}" = "one two three" ]
+}
+
+@test "argument with a glob char is not expanded by on_nodes" {
+    "$ON_NODES" 1 1 ls '*.c'
+    [ "$(forwarded_count)" -eq 2 ]
+    run cat "${ARGV_LOG}"
+    [ "${lines[3]}" = "*.c" ]
+}
+
+@test "empty-string argument is preserved as one argument" {
+    "$ON_NODES" 1 1 echo ""
+    # 'echo' + one empty arg = 2 forwarded args.
+    [ "$(forwarded_count)" -eq 2 ]
+}