docs: add CLI smoke testing example for MCP servers

[jiezeng2004-design]

Summary

Add a CLI smoke testing example document showing how to test MCP servers from the command line using the Inspector's CLI mode. The method is generic and applicable to any MCP server, with the reference server-everything and a local stdio server used as concrete examples.

Type of Change

• Documentation update

Changes Made

• New file docs/cli-smoke-testing-example.md describing a reusable smoke testing workflow built on the existing CLI mode (npx @modelcontextprotocol/inspector --cli ...):
  • The four-step connect / list / call / assert workflow.
  • A table of supported --method values and their required options (matching the CLI source).
  • Two runnable examples: the reference @modelcontextprotocol/server-everything and a local stdio server.
  • Guidance on asserting that outputs do not leak sensitive content, including both a generic block-list check and a server-side guard example.
  • Remote server (SSE / Streamable HTTP) usage and a minimal CI shell script.

The document does not introduce or depend on any external package; the local-server example notes that any MCP server built to a dist/index.js entry point can be substituted.

Testing

• Manual testing performed

Ran prettier --check (the repo's documented formatter, see CONTRIBUTING.md and the lint-staged config) against the new file; it passes after prettier --write. No code or tests are touched, so npm test / npm run test:e2e are unaffected.

Checklist

• Code follows the style guidelines (ran prettier --write on the new file)
• Self-review completed
• Documentation updated