The timeout now bounds the whole call: one deadline at call start, every wait
gets what remains, so a chunk-by-chunk deferred body cannot outlive it. The
response's message id and operation are checked against the request. An
envelope-level OperationFailure is ClientError::Rejected, distinct from the
transport's Unavailable, so a retry on Unavailable cannot loop on a permanent
protocol mismatch. Every call disconnects its session, success or failure.
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
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