feat: support frontend MCP stdio and fix cockpit voice flow

[x-lixu]

Summary

• add standard stdio transport support to the frontend MCP client while preserving Streamable HTTP compatibility
• document stdio configuration and process lifecycle in Chinese and English
• activate cockpit audio synchronously from the user gesture and recover cleanly from capture failures
• correlate cockpit transcript updates by protocol turn and response IDs to prevent duplicate conversation cards

Validation

• frontend MCP config/client tests: 16 passed
• smart cockpit client tests: 19 passed
• smart cockpit lint and production build passed
• repository ESLint passed