Rewrite of the reconnection logic

[nighthawk]

To avoid crash due to duplicate calls to resuming continuation.

Fixes modelcontextprotocol#137

[Copilot]

Pull Request Overview

This PR refactors the reconnection logic to use a unified retry loop with waitForReady() instead of the previous continuation-based handlers, preventing duplicate continuation resumes and crashes.

• Introduces waitForReady() with a withCheckedThrowingContinuation wrapper
• Replaces old handleConnectionReady/Failed/Cancelled and shared reconnection method with a retry loop in connect()
• Removes connectionContinuationResumed tracking and streamlines exponential backoff

[nighthawk]

Testing looks good.