Problem

When a message dispatch fails (provider error, rate limit, empty response), Telegram now sends the user a meaningful fallback message. All other channels silently drop the failure — the user receives nothing and has no way to know something went wrong.

Current behavior per channel

Proposed fix

Add the same fallback pattern to each channel's dispatch site:

1. Track lastError via onError callback and outer try/catch
2. Check delivery state after dispatch (nothing delivered + failure/skip)
3. Send a user-visible message using resolveFailoverReasonFromError + EmptyResponseError routing (same logic as Telegram)

Extract the error-message-selection logic into a shared helper (e.g. src/auto-reply/reply/delivery-fallback.ts) so it isn't duplicated across channel files.

Related

• Introduced in the model-fallback empty-response fix PR (see EmptyResponseError in src/agents/model-fallback.ts)
• resolveFailoverReasonFromError already handles rate-limit / auth / timeout classification