Cached MCP servers on npx still hit npm on every launch

Testing shows npx re-queries the npm registry on every MCP server launch even when the pinned version is already cached. Without network access, Claude Code and Codex time out after about 30 seconds; --prefer-offline or npm_config_prefer_offline starts the server from cache in under two seconds but freezes the cached version.

• npx hard-codes preferOnline: true and ignores npm's five-minute registry cache
• Offline, Claude Code and Codex fail after ~30s; the pinned server connects only after ~70s
• uvx refuses to run a cached package when PyPI is unreachable, failing after 3 retries in 7.3s
• prefer-offline and npm_config_prefer_offline start the server from cache in under 2 seconds