fix(build): address Copilot review for NodeSource repo setup

- ensure nodesource keyring is world-readable for _apt
- assert installed Node major is v22 to avoid Debian Node 18 fallback

Author: root

openclaw_assistant/Dockerfile

@@ -38,10 +38,13 @@ RUN apt-get update && apt-get install -y --no-install-recommends \
 RUN mkdir -p /etc/apt/keyrings \
  && curl -fsSL https://deb.nodesource.com/gpgkey/nodesource-repo.gpg.key \
     | gpg --dearmor -o /etc/apt/keyrings/nodesource.gpg \
+ && chmod 644 /etc/apt/keyrings/nodesource.gpg \
  && echo "deb [signed-by=/etc/apt/keyrings/nodesource.gpg] https://deb.nodesource.com/node_22.x nodistro main" \
     > /etc/apt/sources.list.d/nodesource.list \
  && apt-get update \
  && apt-get install -y --no-install-recommends nodejs \
+ && node -v \
+ && node -v | grep -E '^v22\.' \
  && apt-get clean \
  && rm -rf /var/lib/apt/lists/*