sessions_send timeout/error results were being surfaced as raw warning
messages in Telegram chats because the tool is classified as mutating,
which forces error warnings to always be shown. However, sessions_send
failures are transient inter-session communication issues where the
message may still have been delivered, so they should not leak to users.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>