StreamableHttp transport - resume long running requests

[ihrpr]

Introducing functionality that allows users to resume long-running requests. This feature is useful for scenarios where:

• Tools or processes require extended execution time
• Users need to check progress periodically (e.g., every few hours)
• Continuous client connection for notifications is unnecessary or impractical

Features:

• Clients can pass a session ID to reconnect with an existing session
• Resume and replay: Tools can accept the last event ID to resume from that point, replaying notifications and waiting for responses

[jspahrsummers]

Mostly looks good, just some bikeshedding on the Protocol interface.