Replace the batch-level processRelayEvents call with a per-event
loop wrapped in try/catch. On exception: log event type, messageId,
timestamp, peer origin, and the error message; continue to the next
event.
Previously, a single poison-pill event (e.g., UNIQUE conflict from
a malformed relay payload) would throw, be caught by the outer
try/catch, and block lastSyncedAt from advancing — causing every
future activation to retry the same broken window indefinitely.
The final 'replayed N events' log line now reports '(K skipped due
to errors)' when K > 0, surfacing the count to operators. Individual
event failures are logged via console.error with enough context to
debug or replay manually.
Trade-off documented in docs/systems/federation.md: forward progress
of the sync pipeline takes priority over strict at-least-once
delivery. An event that fails to process is lost to the receiver
unless replayed manually.