fix(ci): isolate agent smoke in namespace-capable helper

scripts/ci/linux-agent-container-smoke.sh

@@ -0,0 +1,37 @@
+#!/usr/bin/env sh
+# Run from the checkout root. Build context is sent to Docker, never bind-mounted.
+set -eu
+command -v docker >/dev/null
+[ "$(docker info --format '{{.OSType}}')" = linux ] || { echo 'A Linux Docker daemon is required for the agent namespace smoke' >&2; exit 1; }
+tmp="$(mktemp -d)"
+name="evofw-linux-smoke-${GITHUB_RUN_ID:-local}-${GITHUB_RUN_ATTEMPT:-1}-$$"
+image=''
+cleanup() {
+  result=$?
+  trap - EXIT HUP INT TERM
+  docker rm -f "$name" >/dev/null 2>&1 || true
+  if [ -n "$image" ]; then docker image rm "$image" >/dev/null 2>&1 || true; fi
+  rm -rf "$tmp"
+  exit "$result"
+}
+trap cleanup EXIT
+trap 'exit 129' HUP
+trap 'exit 130' INT
+trap 'exit 143' TERM
+docker build --file scripts/ci/linux-agent-smoke.Dockerfile --iidfile "$tmp/image-id" .
+image="$(cat "$tmp/image-id")"
+printf '%s\n' "$image" | grep -Eq '^sha256:[0-9a-f]{64}$' || { echo 'Missing immutable helper image ID' >&2; exit 1; }
+set -- docker run --rm --name "$name" --network none \
+  --cap-drop ALL --cap-add SYS_ADMIN --cap-add NET_ADMIN \
+  --security-opt no-new-privileges:true \
+  --read-only --tmpfs /tmp:rw,nosuid,nodev,noexec,size=64m \
+  --pids-limit 256 --cpus 2 --memory 512m
+# docker-default AppArmor denies the mount operations used by unshare/ip-netns.
+# Only this disposable, networkless helper gets the mount-capable exception.
+# Default seccomp remains enabled and adapts to the two granted capabilities.
+security="$(docker info --format '{{json .SecurityOptions}}')"
+if printf '%s' "$security" | grep -q apparmor; then
+  set -- "$@" --security-opt apparmor=unconfined
+fi
+set -- "$@" "$image"
+"$@"