Instead of just exporting env vars (which are ephemeral), the script
now calls 'openclaw config set' to persist each plugin's sensitive
fields (apiKey, tokens, ports, etc.) under plugins.entries.<id>.config.
Config key mapping per plugin is derived from each plugin's
openclaw.plugin.json configSchema. .env.example updated with all
available variables and their corresponding plugin IDs.
scripts/setup-plugins.sh reads sensitive config from .env (gitignored),
initialises submodules, installs npm deps, and runs each plugin's own
install script. Supports --uninstall, --skip-deps, and per-plugin
selection. .env.example documents all available variables.
