Feature request: make stdio shutdown grace periods configurable in `CommandTransport.Close()`

[cruffinoni]

Is your feature request related to a problem? Please describe.
CommandTransport.Close() currently hardcodes a 5s wait after closing stdin before escalating. This follows the MCP spec's "reasonable time" requirement, but the fixed value leads to noticeable delays (e.g., when testing with processes like sleep that never exit quickly).

Describe the solution you'd like
Make this timeout configurable via a TermGrace time.Duration field on CommandTransport. Default should remain 5 * time.Second to preserve current behavior.

Describe alternatives you've considered

• Keeping the hardcoded 5s wait (current behavior) — but this hurts short-lived or test scenarios.
• Manually killing the process from outside — works, but breaks the intended MCP shutdown sequence.

Additional context
The MCP spec requires a shutdown sequence of closing stdin → waiting a reasonable time → sending SIGTERM, but does not prescribe exact durations. Making TermGrace configurable would keep spec compliance while offering flexibility for different environments and use cases.

[jba]

This would be a field on CommandTransport. We'd have to bikeshed the name. TermGrace isn't common in Go. Perhaps TermDuration or TerminateDuration ("term" sounds ambiguous to me between terminal and terminate) or TerminateWait.

[cruffinoni]

Thanks for the clarification on the naming. I agree that TerminateDuration is the clearest choice.

Just to confirm next steps: would you like me to go ahead and open a PR implementing this field on CommandTransport (defaulting to 5 seconds when zero), along with a short test and documentation update? Or do you prefer maintainers handle it once the design is settled?

Either way works for me, I'm happy to contribute the patch if you're open to it.

[jba]

We'd welcome a PR.