[rumpl]

Summary

• Allow the existing supervisor Start method to reconnect after an explicit Stop, without public API changes.
• Wait for session teardown, watcher exit, and late startup-handshake reaping before reusing the shared connector.
• Preserve idempotent/concurrent Stop behavior and context cancellation while waiting to resume.
• Cover repeated stop/start, stop-before-start, delayed watcher teardown, late handshakes, and real MCP stdio subprocess tool calls.

This lets embedders suspend idle MCP transports and let normal agent tool initialization start them on a later turn without rebuilding the chat.