nssh: harden session recovery #11

Bugbot Review

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Final Result: Bugbot completed review and found 1 potential issue.

Request ID: serverGenReqId_10b035cf-32de-4f66-96ae-50f26efd559d

Cursor Bugbot has reviewed your changes and found 1 potential issue.

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^{Reviewed by Cursor Bugbot for commit 148702d. Configure here.}