feat(client): complete native source and release boundary

Complete the Native Client source/audio boundary, strict v5 loopback contract, Browser media lifecycle handling, and non-blocking release checks. Keep unverified platform/physical gates explicit; do not rewrite the Go Server.

deploy/check-release.sh

@@ -0,0 +1,18 @@
+#!/bin/bash
+set -Eeuo pipefail
+
+if [ "$#" -gt 1 ]; then
+  printf 'usage: %s [current-revision-file]\n' "$0" >&2
+  exit 2
+fi
+
+repo_root="$(cd -- "$(dirname -- "${BASH_SOURCE[0]}")/.." && pwd)"
+node="${SCREENER_NODE:-/usr/local/bin/node}"
+current_file="${1:-/opt/screener/current/REVISION}"
+
+if [ ! -x "$node" ]; then
+  printf 'Node runtime is unavailable: %s\n' "$node" >&2
+  exit 2
+fi
+arguments=("$repo_root/scripts/release-update.mjs" "--current-file" "$current_file")
+exec "$node" "${arguments[@]}"