The previous fix made a broken SMTP/Telegram account non-fatal — the
reply gets recorded either way now — but that also made delivery
failures completely invisible: an agent sees their reply "sent"
successfully with no indication the customer never actually received it.
Added messages.deliveryFailed, set whenever the outbound send throws, and
a warning badge on the message bubble so this is now visible instead of
silent.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Gh2UXUQUVBWroWEnn1FLFG
